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Anticestodal action of oxfendazole on Raillietina tetragona in experimentally infected chickens
Br. vet .
1.
i 1981) . 145, 45 8
ANTICESTODAL ACTION OF OXFENDAZOLE ON Raillietina tetragona IN EXPERIMENTALLY INFECTED CHICKENS I . E . M . NURELHUDA, E . E . ELOWNI* and '1 . HASSAN Faculty of Veterinary Science, University of Khartoum, P. 0. Box 32, Khartoum North, Sudan
SUMMARY Oxfendazole was tested against Raillietina tetragona in experimentally infected chickens using single oral doses of 20, 10, 7 . 5, 5, and 2 . 5 mg/kg body weight . The minimal dose of the drug which produced 100% efficacy against immature worms was 10 mg/kg whereas the same effect on the mature parasite was obtained with 7 . 5 mg/kg . Doses lower than these significantly reduce worm burdens. The compound appears to be safe for chickens and a dose of 20 mg/kg (twice the recommended dose) produced no untoward clinical reactions .
INTRODUCTION Many of the older drugs used against chicken tapeworms have been found unsatisfactory mainly because of their relative inefficiency against some of the pathogenic forms of the worms and/or because of their high toxicity (Gibson, 1975) . Although new chemotherapeutic agents against tapeworms in domestic animals have been introduced, no reliable commercial product is available for specific use against tapeworms of chickens . Oxfendazole, a potent anthelmintic of the benzimidazole group, has been used primarily for its activity against nematodes (Barragry, 1984a,ó) . It has also been shown to have satisfactory activity against Moniezia tapeworms in ruminants (Roberson, 1982) . The objective of this study was to test the efficacy of this compound as a cestocide against chicken tapeworms using the fowl cestode Raillietina tetragona as an experimental model .
MATERIALS AND METHODS Birds
White Leghorn chicks were obtained when 2-3 days old from Kuku Poultry Research Unit in Khartoum or were hatched in an incubator in the Department of Parasitology, University of Khartoum . Maintenance
Chicks were raised in the laboratory under conditions preventing accidental infection with tapeworms . They were provided with an authentic commercial grower diet and water ad libitum. Birds were used when they were 3-8 days old . * Correspondence to Dr E . E . Elowni ; present address : Faculty of Veterinary Medicine, Al-Fateh University, P .O . Box 13662, Tripoli, Libya .
OXFENDAZOLE AGAINST CHICKEN TAPEWORMS
45 9
Infection Cysticercoids of Raillietina tetragona were recovered by dissection of naturally infected ants (Pachycondyla sennaarensis) . The required number of larvae, suspended in normal physiological saline, was fed in gelatin capsules to chicks previously starved for 5 hours . Trials with Raillietina cesticillus (Elowni, 1984) had shown this procedure to be effective in establishing a high level of infection and reducing the variability between individual birds in the worm burdens thus established . Treatment Oxfendazole (Systamex) boluses were crushed to a fine powder and the required doses were administered orally to chicks . The drug was tested against both mature (17-day-old) and immature (7-day-old) worms and drug dosage was calculated according to the mean body weight of birds in the groups to be treated . Experimental design The evaluation of the efficacy of oxfendazole was based on the Controlled Test of Moskey & Harwood (1941) . In any particular experiment, birds of the same age and exposed to similar levels of infections were used . Treatments were allocated at random to these birds and respective groups were designated as `treated' or `untreated controls' . Recovery of worms In all experiments birds were sacrificed on day 14 after treatment . By this time, any remnant scolices or stunted worms surviving drug treatment would be expected to regenerate sufficient strobilar tissue and could therefore be easily discerned at necropsy . The intestine of each bird was removed and slit open longitudinally in a shallow tray containing physiological saline . Intestinal sections were transferred to labelled glass jars and placed in a refrigerator at 4 ° C to allow the worms to become detached . Search for scolices and stunted worms was made using a technique similar to that described by Hopkins, Subramanian & Stallard (1972) for recovery of destrobilated Hymenolepis diminuta from the intestine of mice . Analysis of results The worms recovered from each bird were counted and the total recoveries (number of cysticercoids administered to treated or untreated controls and recovered as worms, regardless of worm size) were tested for statistical analysis by the X 2 test, Yates' correction (Siegel, 1956) . Differences were considered significant when PS 0 . 05 . For illustrative purposes, differences between treated and control birds in the number of worms establishing were transformed into percentages using mean index with the formula
(a-b)/a
X
100=% efficacy
where a is the mean number of worms in the controls and b the mean number in treated birds . Only elimination of the entire worm was considered in the calculation of the indicated `efficacy' . RESULTS AND DISCUSSION Treatment of birds with oxfendazole at a dose of 20 mg/kg body weight resulted in complete removal of worms (Table I) . This dose was about twice the dose for poultry as recommended by the suppliers . It was decided to reduce the dose in a graded manner to
460
BRITISH VETERINARY JOURNAL, 143,
determine if there was a relationship between dose and response . The results show that oxfendazole was an efficient compound which completely eliminated susceptible worms ; a dose of 10 mg/kg achieved 100% efficacy against immature worms (Table 1) whereas 7 . 5 mg/kg was the minimum dose that produced 100% efficacy against the mature parasite (Table II) . It seems therefore to be a reliable cestocide for poultry, through a dual mechanism, i .e . lethality due to local contact with the drug and due to recycling into the intestine of those portions of the drug that might have been absorbed into the circulation . This latter mechanism is known to occur against abomasal and intestinal nematodes (Barragry, 1984a) . Table I Effect of oxfendazole on immature (7-day-old) R .
tetragona
Bird group *
No. of birds
Total larvae given
Drugf dosage/ kg
No . of worms recovered
Efficacy
P value
1
T C
8 7
64 56
20 mg
0 16
100% -
<0 . 001
2
T T C
4 5 5
48 60 60
10 mg 2 . 5 mg
0 10 25
100% 60% -
<0 . 001 <0 . 01
3
T T T C
5 5 5 6
100 100 100 120
10 mg 7 .5 mg 5 mg -
1 15 21 62
98 . 1% 71% 59 . 4% -
<0 . 001 <0 . 001 <0-001
4
T T C
6 6 6
120 120 120
5 mg 2 . 5 mg -
6 34 56
89 . 3% 39 . 3% -
<0 . 001 <0 . 01
5
T T C
7 7 8
84 84 96
5 mg 2 . 5 mg -
29 28 47
29 . 5% 31 . 9% -
>0-05 <0-05 -
6
T C
5 7
100 140
7 . 5 mg
1 100
98 . 6% -
<0 . 001
Trial no.
* T,
treated ; C, control . tAdministered on day 7
of infection .
In addition to its potent anticestodal activity, oxfendazole appears to be well tolerated by chickens and doubling the recommended dose produced no clinical reactions on the host, in this respect resembling its safety in other animals (Roberson, 1982) . Furthermore, it produces significant anthelmintic activity in doses lower than those producing 100% efficacy (Tables I, II) . The results suggest that the sensitivity of Raillietina tetragona to oxfendazole is dependent on the age of the parasite, mature worms being more sensitive than immature
OXFENDAZOLE AGAINST CHICKEN TAPEWORMS
46 1
parasites . This is indicated by the difference in the minimum dose levels bringing about total elimination of mature and immature worms and by the differences in parasite survival rates when these worms are exposed to lower doses . Oxfendazole is known to act on parasites by inhibiting the uptake of low molecular weight nutrients and by interfering with their energy-generating metabolism (Roberson, 1982 ; Barragry, 1984a ; Marriner, 1986) . It may be that metabolic activities of mature and immature R . tetragona differ to the extent of affecting the degree of sensitivity of these worms to this compound .
Table II Effect of oxfendazole against mature (17-day-old) R . tetragona
Trial 1
2
Bird* group
No . of birds
Total larvae given
Drugt dosage/ kg
No. of worms recovered
Efficacy
P value
T
T T C
4 5 4 4
80 100 80 80
10 mg 5 mg 2 . 5 mg -
0 11 12 34
100% 74 . 1% 64 . 7% -
<0 . 001 <0 . 001 <0 . 001
T C
5 6
100 120
7 .5 mg -
0 72
100% -
< 0 . 001
*T, treated ; C, control . tAdministered on day 17 of infection .
ACKNOWLEDGEMENTS
We wish to thank Dr A . Hashim, Managing Director, Vetco (Sudan), and Dr D . B . Harker, Coopers Animal Health Ltd, UK, for their interest in this work and for kindly supplying Systamex (oxfendazole) .
REFERENCES T. (1984a) . New Zealand Veterinary ,Journal32 (10), 161 . T. (1984b) . New Zealand Veterinary ,Journal32 (11), 191 . ELOwNI, E . E . (1984) . Journal of Helminthology 58, 287 . GIBSON, T . E . (1975) . Veterinary Anthelmintic Medication . Technical Communication No . 33, 3rd edn, p . 318 . St Albans : Commonwealth Institute of Helminthology . HOPKINS, C . A ., SUBRAMANIAN, G . & STALLARD, H . (1972) . Parasitology64, 401 . MARRINER, S . (1986). The Veterinary Record 118, 181 . MOSKEY, H. E . & HARWOOD, P . D . (1941) . American Journal of Veterinary Research 2, 55 . ROBERSON, E . L. (1982) . In Veterinary Pharmacology and Therapeutics, eds N . H . Booth & L . E . McDonald, 5th edn, p . 803 . Ames : Iowa State University Press . SIEGEL, S . (1956) . Non parametric Statistics for the Behavioral Sciences . New York : McGraw Hill . BARRAGRY, BARRAGRY,
(Accepted for publication 27 October 15188)
1.
i 1981) . 145, 45 8
ANTICESTODAL ACTION OF OXFENDAZOLE ON Raillietina tetragona IN EXPERIMENTALLY INFECTED CHICKENS I . E . M . NURELHUDA, E . E . ELOWNI* and '1 . HASSAN Faculty of Veterinary Science, University of Khartoum, P. 0. Box 32, Khartoum North, Sudan
SUMMARY Oxfendazole was tested against Raillietina tetragona in experimentally infected chickens using single oral doses of 20, 10, 7 . 5, 5, and 2 . 5 mg/kg body weight . The minimal dose of the drug which produced 100% efficacy against immature worms was 10 mg/kg whereas the same effect on the mature parasite was obtained with 7 . 5 mg/kg . Doses lower than these significantly reduce worm burdens. The compound appears to be safe for chickens and a dose of 20 mg/kg (twice the recommended dose) produced no untoward clinical reactions .
INTRODUCTION Many of the older drugs used against chicken tapeworms have been found unsatisfactory mainly because of their relative inefficiency against some of the pathogenic forms of the worms and/or because of their high toxicity (Gibson, 1975) . Although new chemotherapeutic agents against tapeworms in domestic animals have been introduced, no reliable commercial product is available for specific use against tapeworms of chickens . Oxfendazole, a potent anthelmintic of the benzimidazole group, has been used primarily for its activity against nematodes (Barragry, 1984a,ó) . It has also been shown to have satisfactory activity against Moniezia tapeworms in ruminants (Roberson, 1982) . The objective of this study was to test the efficacy of this compound as a cestocide against chicken tapeworms using the fowl cestode Raillietina tetragona as an experimental model .
MATERIALS AND METHODS Birds
White Leghorn chicks were obtained when 2-3 days old from Kuku Poultry Research Unit in Khartoum or were hatched in an incubator in the Department of Parasitology, University of Khartoum . Maintenance
Chicks were raised in the laboratory under conditions preventing accidental infection with tapeworms . They were provided with an authentic commercial grower diet and water ad libitum. Birds were used when they were 3-8 days old . * Correspondence to Dr E . E . Elowni ; present address : Faculty of Veterinary Medicine, Al-Fateh University, P .O . Box 13662, Tripoli, Libya .
OXFENDAZOLE AGAINST CHICKEN TAPEWORMS
45 9
Infection Cysticercoids of Raillietina tetragona were recovered by dissection of naturally infected ants (Pachycondyla sennaarensis) . The required number of larvae, suspended in normal physiological saline, was fed in gelatin capsules to chicks previously starved for 5 hours . Trials with Raillietina cesticillus (Elowni, 1984) had shown this procedure to be effective in establishing a high level of infection and reducing the variability between individual birds in the worm burdens thus established . Treatment Oxfendazole (Systamex) boluses were crushed to a fine powder and the required doses were administered orally to chicks . The drug was tested against both mature (17-day-old) and immature (7-day-old) worms and drug dosage was calculated according to the mean body weight of birds in the groups to be treated . Experimental design The evaluation of the efficacy of oxfendazole was based on the Controlled Test of Moskey & Harwood (1941) . In any particular experiment, birds of the same age and exposed to similar levels of infections were used . Treatments were allocated at random to these birds and respective groups were designated as `treated' or `untreated controls' . Recovery of worms In all experiments birds were sacrificed on day 14 after treatment . By this time, any remnant scolices or stunted worms surviving drug treatment would be expected to regenerate sufficient strobilar tissue and could therefore be easily discerned at necropsy . The intestine of each bird was removed and slit open longitudinally in a shallow tray containing physiological saline . Intestinal sections were transferred to labelled glass jars and placed in a refrigerator at 4 ° C to allow the worms to become detached . Search for scolices and stunted worms was made using a technique similar to that described by Hopkins, Subramanian & Stallard (1972) for recovery of destrobilated Hymenolepis diminuta from the intestine of mice . Analysis of results The worms recovered from each bird were counted and the total recoveries (number of cysticercoids administered to treated or untreated controls and recovered as worms, regardless of worm size) were tested for statistical analysis by the X 2 test, Yates' correction (Siegel, 1956) . Differences were considered significant when PS 0 . 05 . For illustrative purposes, differences between treated and control birds in the number of worms establishing were transformed into percentages using mean index with the formula
(a-b)/a
X
100=% efficacy
where a is the mean number of worms in the controls and b the mean number in treated birds . Only elimination of the entire worm was considered in the calculation of the indicated `efficacy' . RESULTS AND DISCUSSION Treatment of birds with oxfendazole at a dose of 20 mg/kg body weight resulted in complete removal of worms (Table I) . This dose was about twice the dose for poultry as recommended by the suppliers . It was decided to reduce the dose in a graded manner to
460
BRITISH VETERINARY JOURNAL, 143,
determine if there was a relationship between dose and response . The results show that oxfendazole was an efficient compound which completely eliminated susceptible worms ; a dose of 10 mg/kg achieved 100% efficacy against immature worms (Table 1) whereas 7 . 5 mg/kg was the minimum dose that produced 100% efficacy against the mature parasite (Table II) . It seems therefore to be a reliable cestocide for poultry, through a dual mechanism, i .e . lethality due to local contact with the drug and due to recycling into the intestine of those portions of the drug that might have been absorbed into the circulation . This latter mechanism is known to occur against abomasal and intestinal nematodes (Barragry, 1984a) . Table I Effect of oxfendazole on immature (7-day-old) R .
tetragona
Bird group *
No. of birds
Total larvae given
Drugf dosage/ kg
No . of worms recovered
Efficacy
P value
1
T C
8 7
64 56
20 mg
0 16
100% -
<0 . 001
2
T T C
4 5 5
48 60 60
10 mg 2 . 5 mg
0 10 25
100% 60% -
<0 . 001 <0 . 01
3
T T T C
5 5 5 6
100 100 100 120
10 mg 7 .5 mg 5 mg -
1 15 21 62
98 . 1% 71% 59 . 4% -
<0 . 001 <0 . 001 <0-001
4
T T C
6 6 6
120 120 120
5 mg 2 . 5 mg -
6 34 56
89 . 3% 39 . 3% -
<0 . 001 <0 . 01
5
T T C
7 7 8
84 84 96
5 mg 2 . 5 mg -
29 28 47
29 . 5% 31 . 9% -
>0-05 <0-05 -
6
T C
5 7
100 140
7 . 5 mg
1 100
98 . 6% -
<0 . 001
Trial no.
* T,
treated ; C, control . tAdministered on day 7
of infection .
In addition to its potent anticestodal activity, oxfendazole appears to be well tolerated by chickens and doubling the recommended dose produced no clinical reactions on the host, in this respect resembling its safety in other animals (Roberson, 1982) . Furthermore, it produces significant anthelmintic activity in doses lower than those producing 100% efficacy (Tables I, II) . The results suggest that the sensitivity of Raillietina tetragona to oxfendazole is dependent on the age of the parasite, mature worms being more sensitive than immature
OXFENDAZOLE AGAINST CHICKEN TAPEWORMS
46 1
parasites . This is indicated by the difference in the minimum dose levels bringing about total elimination of mature and immature worms and by the differences in parasite survival rates when these worms are exposed to lower doses . Oxfendazole is known to act on parasites by inhibiting the uptake of low molecular weight nutrients and by interfering with their energy-generating metabolism (Roberson, 1982 ; Barragry, 1984a ; Marriner, 1986) . It may be that metabolic activities of mature and immature R . tetragona differ to the extent of affecting the degree of sensitivity of these worms to this compound .
Table II Effect of oxfendazole against mature (17-day-old) R . tetragona
Trial 1
2
Bird* group
No . of birds
Total larvae given
Drugt dosage/ kg
No. of worms recovered
Efficacy
P value
T
T T C
4 5 4 4
80 100 80 80
10 mg 5 mg 2 . 5 mg -
0 11 12 34
100% 74 . 1% 64 . 7% -
<0 . 001 <0 . 001 <0 . 001
T C
5 6
100 120
7 .5 mg -
0 72
100% -
< 0 . 001
*T, treated ; C, control . tAdministered on day 17 of infection .
ACKNOWLEDGEMENTS
We wish to thank Dr A . Hashim, Managing Director, Vetco (Sudan), and Dr D . B . Harker, Coopers Animal Health Ltd, UK, for their interest in this work and for kindly supplying Systamex (oxfendazole) .
REFERENCES T. (1984a) . New Zealand Veterinary ,Journal32 (10), 161 . T. (1984b) . New Zealand Veterinary ,Journal32 (11), 191 . ELOwNI, E . E . (1984) . Journal of Helminthology 58, 287 . GIBSON, T . E . (1975) . Veterinary Anthelmintic Medication . Technical Communication No . 33, 3rd edn, p . 318 . St Albans : Commonwealth Institute of Helminthology . HOPKINS, C . A ., SUBRAMANIAN, G . & STALLARD, H . (1972) . Parasitology64, 401 . MARRINER, S . (1986). The Veterinary Record 118, 181 . MOSKEY, H. E . & HARWOOD, P . D . (1941) . American Journal of Veterinary Research 2, 55 . ROBERSON, E . L. (1982) . In Veterinary Pharmacology and Therapeutics, eds N . H . Booth & L . E . McDonald, 5th edn, p . 803 . Ames : Iowa State University Press . SIEGEL, S . (1956) . Non parametric Statistics for the Behavioral Sciences . New York : McGraw Hill . BARRAGRY, BARRAGRY,
(Accepted for publication 27 October 15188)