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Estimation of the potential demand for a bovine babesiosis and anaplasmosis vaccine in argentina
Veterinary Parasitology, 36 (1990) 131-140 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
131
E s t i m a t i o n of the P o t e n t i a l D e m a n d for a B o v i n e B a b e s i o s i s a n d A n a p l a s m o s i s V a c c i n e in A r g e n t i n a
E.J.A. S P A T H , A.J. M A N G O L D and A.A. G U G L I E L M O N E
Estacidn Experimental Agropecuaria Salta, Instituto Nacional de Tecnologia Agropecuaria, CC 228, 4400 Salta (Argentina) (Accepted for publication 23 November 1989)
ABSTRACT Sp~ith, E.J.A., Mangold, A.J. and Guglielmone, A.A., 1990. Estimation of the potential demand for a bovine babesiosis and anaplasmosis vaccine in Argentina. Vet. Parasitol., 36:131-140. A survey to estimate the potential demand for a bovine babesiosis and anaplasmosis vaccine was carried out by a postal questionnaire sent to 4407 veterinarians in the north and centre of Argentina. Twenty-three percent of the questionnaires (1047) were answered; 317 (7.2% of the total, 30 % of those answered) pointed out the occurrence of the diseases and/or probable demand for the vaccine. The minimum and maximum demands were 407 892 and 982 300 doses for anaplasmosis, and 272 496 and 631 400 doses for babesiosis, respectively. The results presented from here onwards are based on the minimum demand. Sixty-eight and 48% of the anaplasmosis and babesiosis vaccine demand, respectively, came from veterinarians living in the Boophilus micro plus-free area, while the remainder came from the tick-infested area, reflecting the fact that many farm owners from the tick-infested area seek professional assistance from veterinarians living in the tick-free area. Most of the demand for both vaccines was aimed at breeding cattle (77.2%), 14.5% at dairy cattle and the rest at studs (8.3%). Veterinarians living in the tick-infested area demanded vaccine for breeding cattle in a higher proportion than veterinarians from the tick-free area, whose demand was greater for dairy cattle. In the tick-free area, the demand for anaplasmosis vaccine was twice that for babesiosis vaccine, whereas in the tick-infested area the demand was equal. This agrees with the fact that the anaplasmosis-stricken area extends beyond the tickinfested region. Sixty percent of the respondents preferred a vaccine frozen in liquid nitrogen, whilst the rest preferred a refrigerated one, the first group accounted for 73 % of the total demand. Fifty-six percent of the demand occurred between March and June with the peak in April, which reflects the main weaning date. The elasticity of the demand is discussed in relation to the probable benefits to be accrued by the farmers who make use of it. The annual mortality rates due to both babesiosis and anaplasmosis were estimated at 1.5 and 3.5% in the milk herds of Salta and Tucum~n, respectively. In the beef herds of these two provinces, the mortality rate due to both diseases has been estimated at 3.5%. Using these figures and current prices, the systematic application of the vaccine in calves would render a benefit-cost ratio between 4.6 and 9.0, which would warrant its use in the herds of the areas at risk, i.e. in enzootic instability.
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© 1990 Elsevier Science Publishers B.V.
132
E.J.A. SP,~TH ET AL.
INTRODUCTION Bovine babesiosis, caused by Babesia bovis and Babesia bigemina, is transmitted by the cattle tick Boophilus microplus in Argentina. The occurrence of babesiosis is thus limited to the area where the tick is present, which extends over 82 X 106 ha (Signorini and Mattos, 1987) with a population of ~ 12 X 106 cattle (Anon., 1978). The transmission of Anaplasma marginale is more complex; several transmitters, including ticks and biting flies, and husbandry practices are involved. Therefore the occurrence of anaplasmosis extends beyond the limits of the cattle tick-infested area (e.g. Anziani, 1979). It is estimated that in the area at risk of anaplasmosis there is a population of ~ 18X 106 cattle. Countries like Australia, Israel, South Africa and Uruguay partially prevent the losses produced by anaplasmosis and babesiosis by the application of a vaccine based on attenuated B. bovis and B. bigemina and Anaplasma centrale (Guglielmone, 1980). The last organism is of low pathogenicity for cattle and protects against the more severe clinical effects of A. marginale infections. The production of these vaccines in Argentina requires a large investment by the government a n d / o r private laboratories which would be justified if there was a considerable demand. In this paper, we present the results obtained from a survey performed to estimate the potential demand for a vaccine to prevent losses due to bovine babesiosis and anaplasmosis. MATERIALS AND METHODS The survey was carried out by a postal questionnaire sent to veterinarians between October 1986 and April 1987. The list of veterinarians and their addresses was obtained from different sources and our own records. This first list was amended to restrict the survey to those veterinarians working in the area stricken by anaplasmosis and babesiosis, and in regions where cattle studs exist which usually sell breeders (males and females) to the north of the country. The final number of veterinarians selected was 4407, which represents 46% of the total population of veterinarians in Argentina (de Diego, 1985). The questionnaire contained a general and a specific section. The former was designed to characterize the type of activity of those surveyed, namely public or private employment, small or large animal clinic, drug production, teaching. The latter consisted of eight blocks of questions, the first six closed and the last two open. The types of questions were as follows. (1) Existence of anaplasmosis and babesiosis a n d / o r probable demand for a vaccine for cattle to be sent to the risk zone. (2) Minimum and maximum yearly amount of doses required to fulfil a potential demand for farmers who are usually advised. (The cost per dose would
BOVINEBABESIOSISAND ANAPLASMOSISVACCINEDEMAND
133
be equivalent to the price of 2.4 kg liveweight of a steer weighing 401-420 kg, ex-Liniers Market. (Liniers is the largest cattle auction market in Argentina, located in the city of Buenos Aires. About 2.5 million cattle are auctioned yearly. This figure represented 18% of the cattle slaughtered in 1986, therefore the prices reached in Liniers play a leading role in the whole country. ) (3) The production system at whom the vaccines are aimed: breeding cattle, dairy or studs. (4) Seasonality of the demand for vaccines. (It was suggested that the vaccine should be applied only to calves between 4 and 10 months of age, once in their lifetime. ) (5) Preference for preservation method: refrigerated between 4 and 8 ° with a viability of 7 days or frozen in liquid nitrogen with a minimum viability of 1 year. (6) Number of liquid nitrogen containers owned, if any. (7) Reasons why there is no demand if the diseases exist. (8) Free comment. The questionnaires were sent with an explanatory letter and including a selfaddressed, reply-paid envelope. A reminder, consisting of the same questionnaire and a slightly different explanatory letter, was sent 2 months later to
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40 Fig. 1. Minimum potential demand for vaccine against anaplasmosis in Argentina ( • 5000 doses). -,Southern limit of the cattle tick-infested area (1986). 1, Buenos Aires; 2, Catamarca; 3, Cdrdoba; 4, Chaco; 5, Corrientes; 6, Entre Rfos; 7, Formosa; 8, Jujuy; 9, Misiones; 10, Salta; 11, Santiago del Estero; 12, Santa Fe; 13, Tucum4n.
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Fig. 2. Minimum potential demand for vaccine against babesiosis in Argentina ( • 5000 doses). ,Southern limit of the cattle tick-infested area {1986). 1, Buenos Aires; 2, Catamarca; 3, Cdrdoba; 4, Chaco; 5, Corrientes; 6, Entre Rfos; 7, Formosa; 8, Jujuy; 9, Misiones; 10, Salta; 11, Santiago del Estero; 12, Santa Fe; 13, Tucumdn.
those veterinarians who failed to return the questionnaire. For the purpose of the analysis, we considered the tick-infested area as the following provinces: Catamarca, Corrientes, Chaco, Formosa, Jujuy, Misiones, Salta, Santiago del Estero and Tucumdn; and the tick-free area as the rest of the country, even though the limits do not correspond exactly with the limits of the tick eradication campaign (see Figs. 1 and 2). The answers were coded and analysed using a local statistical computer package (SIPDATA, Pellegrini and Fontagnol, 1987) on an IBM S/34 computer. RESULTS
Of the questionnaires sent, 1047 (23.7%) were returned; 338 were positive for a potential demand for vaccine. Twenty-one of these questionnaires were discarded because the respondent held a full-time government post related to animal health (research, disease control or extension) or because of unusual responses. The final number of questionnaires analysed was 317 (7.2%). Furthermore, 303 questionnaires (6.8%) were returned owing to outdated addresses.
BOVINEBABESIOSISAND ANAPLASMOSISVACCINEDEMAND
135
The greatest percentage of usable responses came from the provinces of the northwest, northeast and Santa Fe. The major contribution of usable responses was provided by Santa Fe, C6rdoba and Buenos Aires provinces, with 65% of the total (Table 1). The minimum and maximum potential demand was 407 892 and 982 300 doses for anaplasmosis, and 272 496 and 631 400 doses for babesiosis, respectively. The results from here onwards will be based on the minimum demand. Sixty-eight and 48% of the demand for anaplasmosis and babesiosis vaccine, respectively, came from veterinarians living in the tick-free area, while the other 32 and 52% came from the tick-infested area. More than 60% of the total potential demand originated from the provinces of Santa Fe, Corrientes and Buenos Aires (including the capital in the latter, Figs. 1, 2 and 3a). Most of the demand was aimed at vaccine application in breeding cattle (77.2%), secondly for dairy cattle (14.5%) and finally for cattle studs (8.3%). The number of doses of anaplasmosis vaccine was twice that for babesiosis vaccine in dairy cattle (Fig. 3b). Discriminating this information between veterinarians living in the tickfree and tick-infested areas shows that in the first group there was a relatively higher demand for vaccine for dairy cattle, whilst in the second group the demand was relatively greater for breeding cattle (Fig. 3b). TABLE 1 Number of questionnaires sent and type of response Province
Questionnaires sent
Usable questionnaires
Usable responses from the total received
(n)
(%) n
%
Buenos Aires Catamarca C6rdoba Corrientes Chaco Entre Rfos Formosa Jujuy Misiones Salta Sgo. del Estero Santa Fe Tucum~in
2283 6 576 237 98 245 33 17 55 26 26 766 39
58 1 45 26 18 16 4 5 8 9 10 103 14
2.5 16.7 7.8 11.0 18.4 6.5 12.1 29.4 14.5 34.6 38.5 13.4 35.9
18.3 0.3 14.2 8.2 5.7 5.0 1.3 1.6 2.5 2.8 3.2 32.5 4.4
Total
4407
317
7.2
100.0
136
E.J.A. SPATH ET AL.
Min,mum demand % 80 277291 60
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Fig. 3. M i n i m u m potential d e m a n d for vaccine against anaplasmosis and babesiosis in cattle tickinfested and free zones (a), a n d type of production system (b). D = dairy; B r - - breeding herds; S = cattle studs.
TABLE 2 M i n i m u m potential d e m a n d for type of vaccine ( % ) Preservation
Responses
Anaplasmosis
Babesiosis
Total
Refrigerated Frozen No answer
104 (37) 180 (63) 33
87 636 (25) 257 353 (75) 62 903
66 636 (29) 164 460 (71) 41 400 -
154 272 (27) 421 813 (73) 104 303 -
Total
317
407 892
272 496
680 388
Sixty-three percent of the respondents preferred a frozen vaccine, which accounted for 73% of the total demand (Table 2). The demand showed an autumn peak, 56% occurring between March and June. There were no differences in the seasonality of the demand between vaccines (Fig. 4).
BOVINE BABESIOSIS AND ANAPLASMOSIS VACCINE DEMAND
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DISCUSSION
The response rate is considered adequate, taking into account that 52% of the questionnaires were sent to the province and city of Buenos Aires, where babesiosis does not exist and anaplasmosis is still irrelevant. However, 60% of Argentinian veterinarians live in this area (A. de Diego, personal communication, 1985). Some of them work as consultants in cattle studs that provide breeders to the north of the country or advise the owners of ranches located in the cattle tick-infested area. The high percentage of responses from the northwest, northeast and Santa Fe province stresses the importance of these diseases in these regions, whilst on the other hand the high percentage of usable responses from Buenos Aires, C6rdoba and Santa Fe indicates the large population of veterinarians in these three provinces, which together account for 80% of the total population (A. de Diego, personal communication, 1985). The demand for anaplasmosis vaccines compared with babesiosis vaccines was greater for dairy cattle in the provinces of C6rdoba and Santa Fe, where anaplasmosis occurs frequently (Anziani, 1979 ), reflecting the relevance of the milk industry in these areas. ', With regard to the seasonality of the demand, it only reflects the main weaning date in most of the country, which coincides with the age of the calves suggested to be appropriate for vaccination. There are ~ 2.16 X 106 calves in the area infested with the cattle tick B. microplus (Anon., 1978); this is the maximum number of doses of babesiosis vaccine that could be applied yearly, since it is recommended that it should be applied in calves once in their lifetime between 4 and 10 months of age (Guglielmone, 1990).
138
E.J.A. SPATH ET AL.
In the case of anaplasmosis, the m a x i m u m number of doses to be applied yearly is ~ 50% greater. The minimum potential demand estimated is therefore ~ 13% of the m a x i m u m possible. The demand for a vaccine depends, among other factors, on the expected returns obtained by its application. These are a function of the costs of vaccine application and the cost savings from its adoption. The economic evaluation of a control scheme based on the use of a vaccine can be estimated using partial budget analysis which considers only the components of gross income and the costs of production affected by the use of the vaccine (Morris, 1969; Ellis and James, 1979). On-farm costs can be estimated as the cost of the vaccine plus the fees of the veterinarian since vaccination normally occurs in conjunction with other husbandry practices. The physical effects associated with anaplasmosis and babesiosis in dairy cattle include death, abortion, lower milk production and delay in conception (Programa de las Naciones Unidas para el Desarrollo, 1981 ). The benefits of vaccination are therefore the cost savings of the avoidance of these effects and of the treatment costs. In the Lerma Valley dairy herd, Province of Salta (comprising 78 herds with 10 500 dairy cattle) where the average yearly incidence and mortality rates are 6.5 and 1.5% in cows, respectively, the annual losses associated with both diseases were estimated as 7.7% of the yearly milk production. The benefit-cost ratio of a vaccination programme in replacement females in these herds was estimated as 9:1 (Sp~ith, 1987). In the milking sheds of Tucum~n (with ~ 200 dairy herds and a total dairy cattle population of 20 000 animals ), the yearly mortality rate due to tick fever in cows was estimated at 3.5% (Sp~ith et al., 1979). Although no detailed proTABLE 3
Estimation of savings and costs of vaccination against losses from anaplasmosis and babesiosis in a herd of 100 animals Yearly Mortality I Beef loss due incirate 1 to mortality dence (%) rate
0.5
1.0 1.5 2.0 3.0 4.0 5.0
0.2 0.4 0.6 0.8 1.2 1.6 2.0
II
III
kg
U$S
kg
U$S
63 126 190 252 379 506 632
50.4 100.8 152.0 201.6 303.2 404.8 505.6
11.4 22.8 34.2 45.6 68.4 91.2 114.0
9.1 18.2 27.4 36.5 54.7 73.0 91.2
1Estimated as 40%.
IV
Loss of liveweight Cost of Benefits due to clinical therapy ( I + I I + I I I ) attack (U$S) )40.9
2.4 4.8 7.2 9.6 14.4 19.2 24.0
55.7 111.4 167.9 222.9 335.1 447.3 558.7
V
Benefit
Cost of vaccination
cost
of 28calves
IV/V
84.6 84.6 84.6 84.6 84.6 84.6 84.6
0.66 1.32 1.98 2.63 3.96 5.28 6.60
ratio
BOVINE BABESIOSIS AND ANAPLASMOSIS VACCINE DEMAND
139
d u c t i o n p a r a m e t e r s are available to calculate t h e cost savings due to a vaccin a t i o n p r o g r a m m e in these herds, it is e s t i m a t e d t h a t at least a similar or greater b e n e f i t - c o s t ratio s h o u l d be e x p e c t e d as in the L e r m a Valley. In b e e f cattle, t h e m a i n physical effects can be r e d u c e d to two: weight loss a n d death. T h e average weight of cattle dying f r o m a n a p l a s m o s i s a n d babesiosis in n o r t h w e s t e r n A r g e n t i n a is 316 kg, w h e r e a s t h e average weight loss due to clinical a t t a c k is 12% (i.e. 38 kg). T h e a d d i t i o n a l costs a n d cost savings due to the a p p l i c a t i o n o f a s y s t e m a t i c v a c c i n a t i o n s c h e m e in an average b e e f h e r d of the s o u t h w e s t of Salta a n d n o r t h o f Tucum~in (Sp~ith a n d Mangold, 1986) are s h o w n in T a b l e 3. U n p u b l i s h e d data, o b t a i n e d in the s u r v e y r e p o r t e d in the p a p e r b y Sp~ith a n d M a n g o l d (1986) i n d i c a t e d t h a t the average clinical incidence of tick fever was 3.5% in adult cattle, with a case fatality rate of 40%. W i t h t h e s e figures, t h e b e n e f i t - c o s t ratio would be 4.6:1 ( T a b l e 3). T h e t h r e e e x a m p l e s suggest t h a t u n d e r t h e c o n d i t i o n s in t h e n o r t h w e s t of A r g e n t i n a , w h e r e a large p r o p o r t i o n of the dairy h e r d s a n d ~ 32% of the beef h e r d s are in enzootic i n s t a b i l i t y ( H g b i c h et al., 1982; Sp~ith et al., 1987), the a p p l i c a t i o n of a s y s t e m a t i c v a c c i n a t i o n p r o g r a m m e is w a r r a n t e d . ACKNOWLEDGEMENT We are i n d e b t e d to Drs. A. Abdala, O. Anziani, P. Fr~re, M. GSmez, E. Nogu~s, A. de Diego a n d J. T r i n i d a d for the i n f o r m a t i o n regarding the v e t e r i n a r y p o p u l a t i o n in d i f f e r e n t provinces, to Mr. O.H. G h e r z i a n d D. F o n t a g n o l for the design of the q u e s t i o n n a i r e , a n d to Mr. E. Avil~s for the figures.
REFERENCES Anonymous, 1978. Censo Ganadero 1977. Secretarla de Agricultura y Ganaderfa, Ministerio de Economla, Buenos Aires, 299 pp. Anziani, O.S., 1979. Anaplasmosis en ~reas libres de garrapatas. In: Reunidn Anual de Informacidn T~cnica para Productores. Est. Exp. Reg. Agrop. INTA Rafaela, pp. 63 68. De Diego, A.I., 1985. Din~imica de la profesidn veterinaria en la Argentina. Xo. Congreso Panamericano de Medieina Veterinaria y Zootecnica, 23-27 September 1985, Buenos Aires, Trabajo No. 398. Ellis, P.R. and James, A.D., 1979. The economics of animal health. 2. Economics in farm practice. Vet. Rec., 105: 523-526. Guglielmone, A.A., 1980. La prevencidn de babesiosis y anaplasmosis en Argentina y Australia. Rev. Med. Vet. (Buenos Aires), 61: 275-277. Guglielmone, A.A., 1990. Garrapatas y enfermedades transmitidas por ellas: diez primeros afios de estudio en la Unidad Regional de InvestigaciSn en Sanidad Animal del Noroeste Argentino (URISA-NOA). IDIA, INTA, 58 pp., in press. H~bich, G.E., Gonz~lez de Rfos, L.E., Hadani, A., Condron, R.J., de Haan, L. and Broadbent, D.W., 1982. Estudios sobre sanidad animal en el noroeste argentino. VIII. Prevalencia de animales con anti cuerpos s~ricos contra Babesia bovis yAnaplasma marginale en tambos de Catamarca, Salta y Tucumdn. Rev. Med. Vet. (Buenos Aires), 63: 316-329.
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Morris, R.S., 1969. Assessing the economic value of veterinary services to primary industries. Aust. Vet. J., 45: 295-300. Pellegrini, H.H. and Fontagnol., D.E., 1987. Sistema integral de procesamiento de datos agropecuarios (SIPDATA). An. Instituto Nacional de Tecnologfa Agropecuaria Salta, 1: 15-22. Programa de las Naciones Unidas para el Desarrollo, 1981. Sanidad Animal en la Regi6n Subtropical del Noroeste Argentino. Informe Terminal Proyecto Arg 75/023. Organizaci6n de las Naciones Unidas para la Agricultura y la Alimentaci6n, Roma, 70 pp. Signorini, A.R. and Mattos, C.E., 1987. Hechos sobresalientes en la historia de la erradicaci6n de la garrapata en la Repfiblica Argentina. Consideraciones sociales, socioecon6micas y legales. Consulta de expertos sobre la erradicaci6n de las garrapatas, con referencia especial alas Americas. F.A.O., Mexico, 22-26 June 1987, 31 pp. Sp~ith, E.J.A., 1987. Estimaci6n de las p~rdidas econ6micas producidas por la anaplasmosis y la babesiosis bovina en la cuenca lechera del Valle de Lerma, provincia de Salta. Rev. Med. Vet. (Buenos Aires), 68: 277-282,284-286. Sp~ith, E.J.A. and Mangold, A.J., 1986. Algunas caracterfsticas de produccidn y sanidad en rodeos de ganado bovino de carne en el sudeste de Salta y norte de Tucum~in. Rev. Argent. Prod. Anita., 6: 101-112. Sp~ith, E.J.A., Gonz~lez, R.N., Gonzdlez de Rfos, L., Condron, R.J., Nogu~s, E.M., Guglielmone, A.A., Kiihne, G.I., Broadbent, D.W. and H~ibich, G.E., 1979. Estudios sobre sanidad animal en el noroeste argentino. V. Brucelosis, tuberculosis, tricomoniasis y vibriosis en tambos de Tucumminy otras caracterlsticas sanitarias y de explotaci6n de estos. Gac. Vet., 41:506-517. Sp~th, E.J.A., Guglielmone, A.A. and de Rios, L.G., 1987. Utilizaci6n de un modelo matemgtico simple para evaluar la situaci6n epizootiol6gica de la babesiosis bovina. Rev. Med. Vet. (Buenos Aires), 68: 126-128, 130-131.
131
E s t i m a t i o n of the P o t e n t i a l D e m a n d for a B o v i n e B a b e s i o s i s a n d A n a p l a s m o s i s V a c c i n e in A r g e n t i n a
E.J.A. S P A T H , A.J. M A N G O L D and A.A. G U G L I E L M O N E
Estacidn Experimental Agropecuaria Salta, Instituto Nacional de Tecnologia Agropecuaria, CC 228, 4400 Salta (Argentina) (Accepted for publication 23 November 1989)
ABSTRACT Sp~ith, E.J.A., Mangold, A.J. and Guglielmone, A.A., 1990. Estimation of the potential demand for a bovine babesiosis and anaplasmosis vaccine in Argentina. Vet. Parasitol., 36:131-140. A survey to estimate the potential demand for a bovine babesiosis and anaplasmosis vaccine was carried out by a postal questionnaire sent to 4407 veterinarians in the north and centre of Argentina. Twenty-three percent of the questionnaires (1047) were answered; 317 (7.2% of the total, 30 % of those answered) pointed out the occurrence of the diseases and/or probable demand for the vaccine. The minimum and maximum demands were 407 892 and 982 300 doses for anaplasmosis, and 272 496 and 631 400 doses for babesiosis, respectively. The results presented from here onwards are based on the minimum demand. Sixty-eight and 48% of the anaplasmosis and babesiosis vaccine demand, respectively, came from veterinarians living in the Boophilus micro plus-free area, while the remainder came from the tick-infested area, reflecting the fact that many farm owners from the tick-infested area seek professional assistance from veterinarians living in the tick-free area. Most of the demand for both vaccines was aimed at breeding cattle (77.2%), 14.5% at dairy cattle and the rest at studs (8.3%). Veterinarians living in the tick-infested area demanded vaccine for breeding cattle in a higher proportion than veterinarians from the tick-free area, whose demand was greater for dairy cattle. In the tick-free area, the demand for anaplasmosis vaccine was twice that for babesiosis vaccine, whereas in the tick-infested area the demand was equal. This agrees with the fact that the anaplasmosis-stricken area extends beyond the tickinfested region. Sixty percent of the respondents preferred a vaccine frozen in liquid nitrogen, whilst the rest preferred a refrigerated one, the first group accounted for 73 % of the total demand. Fifty-six percent of the demand occurred between March and June with the peak in April, which reflects the main weaning date. The elasticity of the demand is discussed in relation to the probable benefits to be accrued by the farmers who make use of it. The annual mortality rates due to both babesiosis and anaplasmosis were estimated at 1.5 and 3.5% in the milk herds of Salta and Tucum~n, respectively. In the beef herds of these two provinces, the mortality rate due to both diseases has been estimated at 3.5%. Using these figures and current prices, the systematic application of the vaccine in calves would render a benefit-cost ratio between 4.6 and 9.0, which would warrant its use in the herds of the areas at risk, i.e. in enzootic instability.
0304-4017/90/$03.50
© 1990 Elsevier Science Publishers B.V.
132
E.J.A. SP,~TH ET AL.
INTRODUCTION Bovine babesiosis, caused by Babesia bovis and Babesia bigemina, is transmitted by the cattle tick Boophilus microplus in Argentina. The occurrence of babesiosis is thus limited to the area where the tick is present, which extends over 82 X 106 ha (Signorini and Mattos, 1987) with a population of ~ 12 X 106 cattle (Anon., 1978). The transmission of Anaplasma marginale is more complex; several transmitters, including ticks and biting flies, and husbandry practices are involved. Therefore the occurrence of anaplasmosis extends beyond the limits of the cattle tick-infested area (e.g. Anziani, 1979). It is estimated that in the area at risk of anaplasmosis there is a population of ~ 18X 106 cattle. Countries like Australia, Israel, South Africa and Uruguay partially prevent the losses produced by anaplasmosis and babesiosis by the application of a vaccine based on attenuated B. bovis and B. bigemina and Anaplasma centrale (Guglielmone, 1980). The last organism is of low pathogenicity for cattle and protects against the more severe clinical effects of A. marginale infections. The production of these vaccines in Argentina requires a large investment by the government a n d / o r private laboratories which would be justified if there was a considerable demand. In this paper, we present the results obtained from a survey performed to estimate the potential demand for a vaccine to prevent losses due to bovine babesiosis and anaplasmosis. MATERIALS AND METHODS The survey was carried out by a postal questionnaire sent to veterinarians between October 1986 and April 1987. The list of veterinarians and their addresses was obtained from different sources and our own records. This first list was amended to restrict the survey to those veterinarians working in the area stricken by anaplasmosis and babesiosis, and in regions where cattle studs exist which usually sell breeders (males and females) to the north of the country. The final number of veterinarians selected was 4407, which represents 46% of the total population of veterinarians in Argentina (de Diego, 1985). The questionnaire contained a general and a specific section. The former was designed to characterize the type of activity of those surveyed, namely public or private employment, small or large animal clinic, drug production, teaching. The latter consisted of eight blocks of questions, the first six closed and the last two open. The types of questions were as follows. (1) Existence of anaplasmosis and babesiosis a n d / o r probable demand for a vaccine for cattle to be sent to the risk zone. (2) Minimum and maximum yearly amount of doses required to fulfil a potential demand for farmers who are usually advised. (The cost per dose would
BOVINEBABESIOSISAND ANAPLASMOSISVACCINEDEMAND
133
be equivalent to the price of 2.4 kg liveweight of a steer weighing 401-420 kg, ex-Liniers Market. (Liniers is the largest cattle auction market in Argentina, located in the city of Buenos Aires. About 2.5 million cattle are auctioned yearly. This figure represented 18% of the cattle slaughtered in 1986, therefore the prices reached in Liniers play a leading role in the whole country. ) (3) The production system at whom the vaccines are aimed: breeding cattle, dairy or studs. (4) Seasonality of the demand for vaccines. (It was suggested that the vaccine should be applied only to calves between 4 and 10 months of age, once in their lifetime. ) (5) Preference for preservation method: refrigerated between 4 and 8 ° with a viability of 7 days or frozen in liquid nitrogen with a minimum viability of 1 year. (6) Number of liquid nitrogen containers owned, if any. (7) Reasons why there is no demand if the diseases exist. (8) Free comment. The questionnaires were sent with an explanatory letter and including a selfaddressed, reply-paid envelope. A reminder, consisting of the same questionnaire and a slightly different explanatory letter, was sent 2 months later to
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40 Fig. 1. Minimum potential demand for vaccine against anaplasmosis in Argentina ( • 5000 doses). -,Southern limit of the cattle tick-infested area (1986). 1, Buenos Aires; 2, Catamarca; 3, Cdrdoba; 4, Chaco; 5, Corrientes; 6, Entre Rfos; 7, Formosa; 8, Jujuy; 9, Misiones; 10, Salta; 11, Santiago del Estero; 12, Santa Fe; 13, Tucum4n.
134
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Fig. 2. Minimum potential demand for vaccine against babesiosis in Argentina ( • 5000 doses). ,Southern limit of the cattle tick-infested area {1986). 1, Buenos Aires; 2, Catamarca; 3, Cdrdoba; 4, Chaco; 5, Corrientes; 6, Entre Rfos; 7, Formosa; 8, Jujuy; 9, Misiones; 10, Salta; 11, Santiago del Estero; 12, Santa Fe; 13, Tucumdn.
those veterinarians who failed to return the questionnaire. For the purpose of the analysis, we considered the tick-infested area as the following provinces: Catamarca, Corrientes, Chaco, Formosa, Jujuy, Misiones, Salta, Santiago del Estero and Tucumdn; and the tick-free area as the rest of the country, even though the limits do not correspond exactly with the limits of the tick eradication campaign (see Figs. 1 and 2). The answers were coded and analysed using a local statistical computer package (SIPDATA, Pellegrini and Fontagnol, 1987) on an IBM S/34 computer. RESULTS
Of the questionnaires sent, 1047 (23.7%) were returned; 338 were positive for a potential demand for vaccine. Twenty-one of these questionnaires were discarded because the respondent held a full-time government post related to animal health (research, disease control or extension) or because of unusual responses. The final number of questionnaires analysed was 317 (7.2%). Furthermore, 303 questionnaires (6.8%) were returned owing to outdated addresses.
BOVINEBABESIOSISAND ANAPLASMOSISVACCINEDEMAND
135
The greatest percentage of usable responses came from the provinces of the northwest, northeast and Santa Fe. The major contribution of usable responses was provided by Santa Fe, C6rdoba and Buenos Aires provinces, with 65% of the total (Table 1). The minimum and maximum potential demand was 407 892 and 982 300 doses for anaplasmosis, and 272 496 and 631 400 doses for babesiosis, respectively. The results from here onwards will be based on the minimum demand. Sixty-eight and 48% of the demand for anaplasmosis and babesiosis vaccine, respectively, came from veterinarians living in the tick-free area, while the other 32 and 52% came from the tick-infested area. More than 60% of the total potential demand originated from the provinces of Santa Fe, Corrientes and Buenos Aires (including the capital in the latter, Figs. 1, 2 and 3a). Most of the demand was aimed at vaccine application in breeding cattle (77.2%), secondly for dairy cattle (14.5%) and finally for cattle studs (8.3%). The number of doses of anaplasmosis vaccine was twice that for babesiosis vaccine in dairy cattle (Fig. 3b). Discriminating this information between veterinarians living in the tickfree and tick-infested areas shows that in the first group there was a relatively higher demand for vaccine for dairy cattle, whilst in the second group the demand was relatively greater for breeding cattle (Fig. 3b). TABLE 1 Number of questionnaires sent and type of response Province
Questionnaires sent
Usable questionnaires
Usable responses from the total received
(n)
(%) n
%
Buenos Aires Catamarca C6rdoba Corrientes Chaco Entre Rfos Formosa Jujuy Misiones Salta Sgo. del Estero Santa Fe Tucum~in
2283 6 576 237 98 245 33 17 55 26 26 766 39
58 1 45 26 18 16 4 5 8 9 10 103 14
2.5 16.7 7.8 11.0 18.4 6.5 12.1 29.4 14.5 34.6 38.5 13.4 35.9
18.3 0.3 14.2 8.2 5.7 5.0 1.3 1.6 2.5 2.8 3.2 32.5 4.4
Total
4407
317
7.2
100.0
136
E.J.A. SPATH ET AL.
Min,mum demand % 80 277291 60
407892 130601
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Fig. 3. M i n i m u m potential d e m a n d for vaccine against anaplasmosis and babesiosis in cattle tickinfested and free zones (a), a n d type of production system (b). D = dairy; B r - - breeding herds; S = cattle studs.
TABLE 2 M i n i m u m potential d e m a n d for type of vaccine ( % ) Preservation
Responses
Anaplasmosis
Babesiosis
Total
Refrigerated Frozen No answer
104 (37) 180 (63) 33
87 636 (25) 257 353 (75) 62 903
66 636 (29) 164 460 (71) 41 400 -
154 272 (27) 421 813 (73) 104 303 -
Total
317
407 892
272 496
680 388
Sixty-three percent of the respondents preferred a frozen vaccine, which accounted for 73% of the total demand (Table 2). The demand showed an autumn peak, 56% occurring between March and June. There were no differences in the seasonality of the demand between vaccines (Fig. 4).
BOVINE BABESIOSIS AND ANAPLASMOSIS VACCINE DEMAND
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DISCUSSION
The response rate is considered adequate, taking into account that 52% of the questionnaires were sent to the province and city of Buenos Aires, where babesiosis does not exist and anaplasmosis is still irrelevant. However, 60% of Argentinian veterinarians live in this area (A. de Diego, personal communication, 1985). Some of them work as consultants in cattle studs that provide breeders to the north of the country or advise the owners of ranches located in the cattle tick-infested area. The high percentage of responses from the northwest, northeast and Santa Fe province stresses the importance of these diseases in these regions, whilst on the other hand the high percentage of usable responses from Buenos Aires, C6rdoba and Santa Fe indicates the large population of veterinarians in these three provinces, which together account for 80% of the total population (A. de Diego, personal communication, 1985). The demand for anaplasmosis vaccines compared with babesiosis vaccines was greater for dairy cattle in the provinces of C6rdoba and Santa Fe, where anaplasmosis occurs frequently (Anziani, 1979 ), reflecting the relevance of the milk industry in these areas. ', With regard to the seasonality of the demand, it only reflects the main weaning date in most of the country, which coincides with the age of the calves suggested to be appropriate for vaccination. There are ~ 2.16 X 106 calves in the area infested with the cattle tick B. microplus (Anon., 1978); this is the maximum number of doses of babesiosis vaccine that could be applied yearly, since it is recommended that it should be applied in calves once in their lifetime between 4 and 10 months of age (Guglielmone, 1990).
138
E.J.A. SPATH ET AL.
In the case of anaplasmosis, the m a x i m u m number of doses to be applied yearly is ~ 50% greater. The minimum potential demand estimated is therefore ~ 13% of the m a x i m u m possible. The demand for a vaccine depends, among other factors, on the expected returns obtained by its application. These are a function of the costs of vaccine application and the cost savings from its adoption. The economic evaluation of a control scheme based on the use of a vaccine can be estimated using partial budget analysis which considers only the components of gross income and the costs of production affected by the use of the vaccine (Morris, 1969; Ellis and James, 1979). On-farm costs can be estimated as the cost of the vaccine plus the fees of the veterinarian since vaccination normally occurs in conjunction with other husbandry practices. The physical effects associated with anaplasmosis and babesiosis in dairy cattle include death, abortion, lower milk production and delay in conception (Programa de las Naciones Unidas para el Desarrollo, 1981 ). The benefits of vaccination are therefore the cost savings of the avoidance of these effects and of the treatment costs. In the Lerma Valley dairy herd, Province of Salta (comprising 78 herds with 10 500 dairy cattle) where the average yearly incidence and mortality rates are 6.5 and 1.5% in cows, respectively, the annual losses associated with both diseases were estimated as 7.7% of the yearly milk production. The benefit-cost ratio of a vaccination programme in replacement females in these herds was estimated as 9:1 (Sp~ith, 1987). In the milking sheds of Tucum~n (with ~ 200 dairy herds and a total dairy cattle population of 20 000 animals ), the yearly mortality rate due to tick fever in cows was estimated at 3.5% (Sp~ith et al., 1979). Although no detailed proTABLE 3
Estimation of savings and costs of vaccination against losses from anaplasmosis and babesiosis in a herd of 100 animals Yearly Mortality I Beef loss due incirate 1 to mortality dence (%) rate
0.5
1.0 1.5 2.0 3.0 4.0 5.0
0.2 0.4 0.6 0.8 1.2 1.6 2.0
II
III
kg
U$S
kg
U$S
63 126 190 252 379 506 632
50.4 100.8 152.0 201.6 303.2 404.8 505.6
11.4 22.8 34.2 45.6 68.4 91.2 114.0
9.1 18.2 27.4 36.5 54.7 73.0 91.2
1Estimated as 40%.
IV
Loss of liveweight Cost of Benefits due to clinical therapy ( I + I I + I I I ) attack (U$S) )40.9
2.4 4.8 7.2 9.6 14.4 19.2 24.0
55.7 111.4 167.9 222.9 335.1 447.3 558.7
V
Benefit
Cost of vaccination
cost
of 28calves
IV/V
84.6 84.6 84.6 84.6 84.6 84.6 84.6
0.66 1.32 1.98 2.63 3.96 5.28 6.60
ratio
BOVINE BABESIOSIS AND ANAPLASMOSIS VACCINE DEMAND
139
d u c t i o n p a r a m e t e r s are available to calculate t h e cost savings due to a vaccin a t i o n p r o g r a m m e in these herds, it is e s t i m a t e d t h a t at least a similar or greater b e n e f i t - c o s t ratio s h o u l d be e x p e c t e d as in the L e r m a Valley. In b e e f cattle, t h e m a i n physical effects can be r e d u c e d to two: weight loss a n d death. T h e average weight of cattle dying f r o m a n a p l a s m o s i s a n d babesiosis in n o r t h w e s t e r n A r g e n t i n a is 316 kg, w h e r e a s t h e average weight loss due to clinical a t t a c k is 12% (i.e. 38 kg). T h e a d d i t i o n a l costs a n d cost savings due to the a p p l i c a t i o n o f a s y s t e m a t i c v a c c i n a t i o n s c h e m e in an average b e e f h e r d of the s o u t h w e s t of Salta a n d n o r t h o f Tucum~in (Sp~ith a n d Mangold, 1986) are s h o w n in T a b l e 3. U n p u b l i s h e d data, o b t a i n e d in the s u r v e y r e p o r t e d in the p a p e r b y Sp~ith a n d M a n g o l d (1986) i n d i c a t e d t h a t the average clinical incidence of tick fever was 3.5% in adult cattle, with a case fatality rate of 40%. W i t h t h e s e figures, t h e b e n e f i t - c o s t ratio would be 4.6:1 ( T a b l e 3). T h e t h r e e e x a m p l e s suggest t h a t u n d e r t h e c o n d i t i o n s in t h e n o r t h w e s t of A r g e n t i n a , w h e r e a large p r o p o r t i o n of the dairy h e r d s a n d ~ 32% of the beef h e r d s are in enzootic i n s t a b i l i t y ( H g b i c h et al., 1982; Sp~ith et al., 1987), the a p p l i c a t i o n of a s y s t e m a t i c v a c c i n a t i o n p r o g r a m m e is w a r r a n t e d . ACKNOWLEDGEMENT We are i n d e b t e d to Drs. A. Abdala, O. Anziani, P. Fr~re, M. GSmez, E. Nogu~s, A. de Diego a n d J. T r i n i d a d for the i n f o r m a t i o n regarding the v e t e r i n a r y p o p u l a t i o n in d i f f e r e n t provinces, to Mr. O.H. G h e r z i a n d D. F o n t a g n o l for the design of the q u e s t i o n n a i r e , a n d to Mr. E. Avil~s for the figures.
REFERENCES Anonymous, 1978. Censo Ganadero 1977. Secretarla de Agricultura y Ganaderfa, Ministerio de Economla, Buenos Aires, 299 pp. Anziani, O.S., 1979. Anaplasmosis en ~reas libres de garrapatas. In: Reunidn Anual de Informacidn T~cnica para Productores. Est. Exp. Reg. Agrop. INTA Rafaela, pp. 63 68. De Diego, A.I., 1985. Din~imica de la profesidn veterinaria en la Argentina. Xo. Congreso Panamericano de Medieina Veterinaria y Zootecnica, 23-27 September 1985, Buenos Aires, Trabajo No. 398. Ellis, P.R. and James, A.D., 1979. The economics of animal health. 2. Economics in farm practice. Vet. Rec., 105: 523-526. Guglielmone, A.A., 1980. La prevencidn de babesiosis y anaplasmosis en Argentina y Australia. Rev. Med. Vet. (Buenos Aires), 61: 275-277. Guglielmone, A.A., 1990. Garrapatas y enfermedades transmitidas por ellas: diez primeros afios de estudio en la Unidad Regional de InvestigaciSn en Sanidad Animal del Noroeste Argentino (URISA-NOA). IDIA, INTA, 58 pp., in press. H~bich, G.E., Gonz~lez de Rfos, L.E., Hadani, A., Condron, R.J., de Haan, L. and Broadbent, D.W., 1982. Estudios sobre sanidad animal en el noroeste argentino. VIII. Prevalencia de animales con anti cuerpos s~ricos contra Babesia bovis yAnaplasma marginale en tambos de Catamarca, Salta y Tucumdn. Rev. Med. Vet. (Buenos Aires), 63: 316-329.
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Morris, R.S., 1969. Assessing the economic value of veterinary services to primary industries. Aust. Vet. J., 45: 295-300. Pellegrini, H.H. and Fontagnol., D.E., 1987. Sistema integral de procesamiento de datos agropecuarios (SIPDATA). An. Instituto Nacional de Tecnologfa Agropecuaria Salta, 1: 15-22. Programa de las Naciones Unidas para el Desarrollo, 1981. Sanidad Animal en la Regi6n Subtropical del Noroeste Argentino. Informe Terminal Proyecto Arg 75/023. Organizaci6n de las Naciones Unidas para la Agricultura y la Alimentaci6n, Roma, 70 pp. Signorini, A.R. and Mattos, C.E., 1987. Hechos sobresalientes en la historia de la erradicaci6n de la garrapata en la Repfiblica Argentina. Consideraciones sociales, socioecon6micas y legales. Consulta de expertos sobre la erradicaci6n de las garrapatas, con referencia especial alas Americas. F.A.O., Mexico, 22-26 June 1987, 31 pp. Sp~ith, E.J.A., 1987. Estimaci6n de las p~rdidas econ6micas producidas por la anaplasmosis y la babesiosis bovina en la cuenca lechera del Valle de Lerma, provincia de Salta. Rev. Med. Vet. (Buenos Aires), 68: 277-282,284-286. Sp~ith, E.J.A. and Mangold, A.J., 1986. Algunas caracterfsticas de produccidn y sanidad en rodeos de ganado bovino de carne en el sudeste de Salta y norte de Tucum~in. Rev. Argent. Prod. Anita., 6: 101-112. Sp~ith, E.J.A., Gonz~lez, R.N., Gonzdlez de Rfos, L., Condron, R.J., Nogu~s, E.M., Guglielmone, A.A., Kiihne, G.I., Broadbent, D.W. and H~ibich, G.E., 1979. Estudios sobre sanidad animal en el noroeste argentino. V. Brucelosis, tuberculosis, tricomoniasis y vibriosis en tambos de Tucumminy otras caracterlsticas sanitarias y de explotaci6n de estos. Gac. Vet., 41:506-517. Sp~th, E.J.A., Guglielmone, A.A. and de Rios, L.G., 1987. Utilizaci6n de un modelo matemgtico simple para evaluar la situaci6n epizootiol6gica de la babesiosis bovina. Rev. Med. Vet. (Buenos Aires), 68: 126-128, 130-131.