Rabies control in the Republic of the Philippines: benefits and costs of elimination

Rabies control in the Republic of the Philippines: benefits and costs of elimination D a n i e l B. F i s h b e i n *§§, N o e l J. M i r a n d a * , P e t e r Merrill $, R o l a n d o A. C a m b a ~, M a r t i n M e l t z e r ; E n r l q u e T. C a r l o s , C o n s o l a c l o n F. B a u t l s t a , P.V. S o p u n g c o * * , L y d i a C. M a n g a h a s ~L, L e d a M . H e r n a n d e z '~, M a r y l i n M . L e o n c i o 'T, D o l o r e s M e r c a d o * * , S u s a n Gregorio**, E u m e l i a Salva**, J a m e s G. D o b b i n s * a n d W i l l i a m G. W i n k l e r $$ •

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We compared the benefits and costs o f eliminating animal and human rabies in the Philippines. I f rabies had been eliminated in 1988, economic benefits would total P52.8 (US$2.5) million in 1989. These benefits would largely arise from the abolition o f expenses associated with rabies prevention: P29.7 (US$1.4) million for animal vaccination, P21.6 (US$1.O) million for human postexposure prophylaxis, and PO.3 (US$0.02) million for animal rabies examinations. Benefits also included P1.2 (US$0.06) million in additional earnings o f humans whose death due to rabies would be prevented. Nationwide elimination was estimated to cost between P88.1 (US$4.2) million and P317.2 (US$15.0) million, assuming a canine-to-human ratio of 1:10, vaccine coverage of 60%, and a cost per vaccination of no less than P25 (US$1.19) and no more than P90 (US$4.27). These costs would be recouped 4.1-11.0 years after the initiation o f a one-year elimination campaign. A sensitivity analysis showed that an elimination programme would be economically beneficial in all but the most extreme cases. Keywords:Rabies; elimination;programme;cost-benefitanalysis; Philippines;rabies vaccine;dog diseases INTRODUCTION The mass application of canine rabies vaccines has successfully eliminated the disease in a number of industrialized countries and at least one developing country, and markedly reduced the number of canine and human rabies cases in many other countries and geographical areas I 3. Although early canine rabies control programmes included stray dog control and removal, these practices are no longer considered necessary or effective 4. In countries without wildlife

*Division of Viral and Rickettsial Diseases, Center for Infectious Diseases, Centers for Disease Control, Public Health Service, US Department of Health and Human Services, 1600 Clifton Road, Atlanta, GA 30333, USA. *Research Institute for Tropical Medicine, Department of Health, Republic of Philippines. tPrice Waterhouse Inc., Washington, DC, USA. §Bureau of Animal Industries, Department of Agriculture, Republic of Philippines. ~College of Veterinary Medicine, University of Florida, Gainesville, LA, USA. "National Rabies Committee, Bureau of Animal Industry, Manila, Republic of Philippines. "Office of Public Health Services, Department of Health. **Biologics Production Service, Department of Health. **Field Epidemiology Training Program, Department of Health, Manila, Republic of Philippines. ~t5472 Hugh Howell Rd, Stone Mountain, GA 30087, USA. §§To whom correspondence should be addressed. (Received 3 December 1990; revised 21 February 1991; accepted 22 February 1991) 0264-410X/91/080581~7 © 1991 Butterworth-HeinemannLtd

rabies, elimination of canine rabies results in direct economic savings by allowing the discontinuation of all animal and human rabies prevention programmes, except for quarantine of imported animals s. In areas completely free of rabies, humans bitten by domestic or wild animals do not receive rabies postexposure prophylaxis and domestic animals do not require rabies vaccination 6. In Asia, the success of canine rabies control programmes has been limited; of the 26000 human rabies deaths reported worldwide each year, most occur in the developing countries in Asia 7. Because exposures to potentially rabid dogs are so common in these countries, postexposure treatments are administered at a rate of about 1000 per million population 7, about ten times that in the United States 8. In these developing countries, inexpensive vaccines of adult nervous-tissue origin are readily available, but often cause serious neurological reactions. Vaccines of tissue-culture origin, while free of significant adverse reactions, must often be imported and are extremely expensive; their use depletes limited personal and public health resources, and adversely affects the national balance of payments. In countries where canine rabies is endemic, costeffectiveness studies have demonstrated that dog rabies elimination is more economical than the widespread use of tissue-culture vaccines 4. However, policy makers in Asian countries are most often faced with a different decision: whether to fund and implement rabies control programmes or to maintain the existing rabies prevention activities, which usually include human postexposure

Vaccine, Vol. 9, August 1991 581

Benefits and costs of rabies elimination: D.B. Fishbein et al.

treatment with nervous tissue-derived vaccines and limited canine vaccination. In the Republic of the Philippines, rabies elimination is a desirable and realistic goal for several reasons. The magnitude of the problem is great; when human rabies was last included in national health statistics in 1984 and 1985, the rates of disease (0.55 and 0.58 cases per 100000, respectively) exceeded those found in all but five countries included in a recent global s u r v e f . Efforts to eliminate rabies are facilitated by the absence of wildlife reservoirs 9. The country's island composition would permit regional or phased elimination programmes, and its ocean borders would help prevent reintroduction of the disease once it was eliminated. Despite model control programmes and epidemiological studies of the disease in humans and animals in the 1960s and 1970s 9 11, the number of animal and human rabies cases in the Philippines has changed little in the last half of the twentieth century. Although many reasons can be suggested why canine rabies has not been controlled 12"13, one possible explanation is that the cost of rabies elimination programmes exceeds their economic benefits or the economic benefits of programmes to control other human diseases. To determine if the cost of rabies elimination is excessive, we estimated the expenses related to the prevention and control of human and animal rabies in the Philippines during 1988. Using 1988 expenses as a baseline, we then calculated the cost and economic benefits of eliminating the disease. METHODS

Economic benefits of elimination The economic benefits of rabies elimination were divided into two categories: the discontinuation of expenditure for prevention of the disease in humans and animals, and the additional earnings associated with decreased human mortality due to the disease. Expenditure on rabies control and prevention in the Philippines during 1988 was divided into five components: animal vaccination and population reduction; laboratory diagnosis; postexposure treatment of humans; epidemiology and research; and animal import controls.

Animal vaccination and population control For domestically produced animal vaccine, the costs of production and distribution were obtained from the Biologics Production Service, Department of Health (DOH). The estimated number of imported doses was obtained from the Bureau of Animal Industry, Department of Agriculture, and wholesale costs of these vaccines were provided by veterinary pharmacies. Information about the fees charged by private veterinarians and the cost of the limited dog vaccination campaigns conducted by government and voluntary non-government agencies was obtained by interviewing representatives of these groups. Department of Agriculture officials were interviewed to determine the extent and cost of animal population control programmes.

Laboratory diagnosis The expense of rabies diagnostic testing was calculated from the cost of reagents and salaries at two laboratories (one with a large volume and one with a small volume

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of tests) in Manila. Shipping charges for specimens were also estimated.

Postexposure treatment of humans The number of doses of domestically produced rabies vaccine for humans was obtained from the Biologics Production Service, D O H , as was the number of doses distributed. Since no surveillance on the number of persons vaccinated in the Philippines is conducted, the number of postexposure treatments was estimated by obtaining data on the number of doses of rabies vaccine and immunoglobulin produced or imported and by reviewing the records at the country's largest public vaccination clinic. The rate of postexposure treatments in the geographical area served by this clinic was calculated. The retail cost and number of doses of imported tissue-culture vaccines and rabies immunoglobulins were obtained from distributors of these rabies biologicals and from the Bureau of Food and Drugs, DOH. When specific sales figures were not provided, we assumed that a minimum quantity (200 doses) of each imported vaccine or immunoglobulin was sold.

Epidemiology, research and animal import controls Costs for epidemiology and research were identified from the budgets of the government agencies responsible for rabies surveillance and research in the Philippines. Costs related to the control of imported animals capable of transmitting rabies were sought from the government agencies responsible for the regulation of animal importation.

Earnings of persons whose death would be prevented Because age-specific mortality rates for 1988 were not available, we used the age-specific data for the years 1983 1986. The expected future lifetime earnings of all persons dying of rabies were calculated; the earnings of persons under 15 were not included until the year that they would have attained this age, the earnings of persons over the age of 45 were excluded because their earnings become limited by other diseases and disabilities. Since data regarding the socio-economic status and earnings of the patients with rabies was not available, we assumed that the annual income of each of these patients would equal the per capita gross national income (P12704 in 198814). We assumed benefits would start to accrue in the year after the elimination campaign. For each subsequent year, the earnings of an additional group of adults were added to the cash flow of elimination benefits.

Cost of eliminating rabies The cost of eliminating rabies was calculated as follows: Dog population x % vaccinated x cost per vaccinated dog where canine population is an estimate of the canine population in the Philippines, proportion vaccinated is the proportion of the population that would be vaccinated in an elimination campaign, and cost per vaccinated dog is the cost (including vaccine, labour, supplies, transportation and overheads) of vaccinating one dog with a single dose of rabies vaccine in a nationwide elimination campaign.

Benefits and costs of rabies elimination: D.B. Fishbein et al.

For our estimates of the cost of eliminating the disease, we used a set of initial programme parameters; these parameters were subsequently varied in a sensitivity analysis. The canine population was initially estimated by assuming a dog-to-human ratio of 1:1011 and a human population of 58 750000 on 1 July 198814; ratios of 1:5 and 1:15 were also used in the sensitivity analysis. Between 60 and 80% of a canine population needs to be immunized to prevent further transmission of the disease2"4'11; we therefore varied these two proportions in our initial and sensitivity analyses. We assumed that a complete nationwide campaign would be conducted in a single year by mass dog vaccination campaigns. We calculated a minimum (P25 [US$1.19]) and maximum (P90 [US$4.27]) cost (vaccine, labour, supplies, transportation and overheads) to vaccinate a single dog in these campaigns. The minimum cost per vaccinated dog was based on the cost of vaccinating dogs in the public sector during small-scale campaigns on various islands in the Philippines in 1988; this cost was similar to estimates of the average cost (per dog) of public sector-based rabies elimination campaigns in other countries 4. The maximum cost per dog was based on the cost of vaccinating dogs in the private sector in the Philippines, and was similar to the highest estimates of cost (per dog) of campaigns proposed in other countries (Dog Rabies Elimination, National Programme of the United Republic of Tanzania, Veterinary Public Health Unit, World Health Organisation [unpublished]).

Cost-benefit and sensitivity analysis Using 1988 expenses as a baseline and the 1988 discount rate in the Philippines of 8.94% 14, we compared the cost of a rabies elimination programme with the benefits of eliminating the disease, the present value of the future costs of programmes that would be discontinued and lives that would be saved following elimination. In this analysis, we assumed that during the one-year campaign the costs of rabies prevention (identified above) for vaccination of dogs and humans and diagnosis of animals would not change, that the economic benefits of elimination would not begin to accrue until after this one-year campaign and that after the campaign, there would be no additional expenses related to the prevention of rabies. In the sensitivity analysis we calculated the internal rate of return, discount period (the time in which the cost of a rabies elimination programme would be recouped), and cumulative net present value (for a 25-year period) of a nationwide elimination programme. We varied the

Table 1

ratio of dogs to humans (1:5, 1:10 and 1:15), the percentage of dogs that would be vaccinated in an elimination (60 and 80%), and the discount rate (8.94 and 15%). RESULTS Animal vaccination and population control expenses The expenses associated with animal vaccination in 1988 were estimated to be P29.7 (US$1.4)* million (P505 [US$23.94] per 1000 population) (Table 1 ). This estimate included the cost of imported animal rabies vaccines, the production costs of domestically produced vaccines, and the expenses or fees associated with the administration of these products. There were no public expenditures for stray dog or dog population control programmes. In 1988, distributors obtained permits to import 739 200 doses of tissue culture derived animal rabies vaccines; the actual number of doses imported was not known, but was estimated to be about 500 000. Of these, the number of doses sold (and therefore presumed to be administered) was estimated to be 397 000. Six vaccines were used: Rabisin (Rhone Poulenc, Lyon, France), Rabguard-TC (Norden Laboratories, Lincoln, Nebraska, USA), Rabdumun (Cooper Health Products, Aylesbury, UK), Rabvac (Premium Agro-vet Fromm Lab Inc., Charles City, Iowa, USA), Nob Vac Rabies (Dalton Supplies, Henley-on-Thames, UK), and Dog Vac Rabia (Rodel Chem, Laboratories Ovejero, Madrid, Spain)*. Wholesale costs of these vaccines ranged from P20 (US$0.95) (cost to the government) to P43 (US$2.03) (cost to private veterinarians) per dose. In addition, 8700 two-dose vials of a low egg passage (LEP) vaccine were produced by the Biologics Production Service, DOH; the production cost of the LEP vaccine was P9.54 (US$0.45) per dose (P19.07 [US$0.90] per two-dose vial). This vaccine was distributed free of charge until production was permanently discontinued in early 1988 because of its excessive cost and low potency compared with imported products. About 75% of the canine rabies vaccine used in the Philippines is administered by private veterinarians throughout the country for a total fee of P80 (US$3.79) to P100 (US$4.74) per dose (which includes the cost of vaccine, supplies for its. administration, overheads and profit). The remainder of the vaccine is administered in small campaigns conducted * We used the average exchange rate during 1988 (P21.095 = US $1 ) to convert Philippine pesos to US dollars. +Use of trade names is for identification only and does not imply endorsement by the Public Health Service or by the US Department of Health and Human Services

Estimated e x p e n s e s a associated with canine rabies prevention, Philippines, 1988 Private sector b

Public sector

Total

Expense component

Doses

Expense

Doses

Expense

Doses

Expense

Canine vaccines Domestic Im ported Total biologicals Vaccine administration cost Total

17 340 97 000 114 340 114 340

165 340 1 940 000 2 105 340 571 700 2 677 040

300 00O 300 000 300 000

12 000 000 12 000 000 15 0O0 000 27 000 000

17 340 397 000 414 340 414 340

165 340 13 940 000 14 105 340 15 571 700 29 677 040

aAII expenses in Philippine pesos (average 1988 exchange rate: P21.09=US$1). bAll expenses not incurred by the government. Clncludes all expenses and professional charges except the cost of the biologicals

Vaccine, Vol. 9, August 1991 583

Benefits and costs of rabies elimination: D.B. Fishbein et al. Table 2

Estimated

expenses a associated

with human postexposure treatment, Philippines, 1988 Public sector

Expense component Vaccines Domestic Imported Immune globulin Imported Total biologicals Vaccination administration c Total e x p e n s e s

Doses

Expense

256 000

Private sector ~ Doses

634880

-

19150 -

256000 256000

634880 1152 000 1786880

2 841 21 991 21 991

Expense

Total

Doses

Expense

8124 550

256 000 19 150

634880 8124 550

6 940 068 15064 618 4684 083 19748701

2 841 275150 277991

6 940068 15699 498 5836083 21 535581

aAII expenses in Philippine pesos (average 1988 exchange rate: P21.09= US$1). ~AII expenses not incurred by the government. Clncludes all expenses and professional charges except the cost of the biologicals

by the Philippine government or private v o l u n t a r y agencies, at a total cost (including the cost of the vaccine, supplies, salaries and transportation) of P25 (US$1.19) per dose.

Postexposure treatment of humans About 42000 persons begin rabies postexposure prophylaxis in the Philippines each year. The total cost of postexposure prophylaxis was estimated to be P21.6 (US$1.0) million (P366 [US$17.35]/1000 population)

(Table 2). Filipinos who m a y have been exposed to rabies are treated with either a domestically produced vaccine made from the brains of adult goats (Semple vaccine, nerve tissue vaccine [NTV]) or one of three imported vaccines of tissue culture origin: human diploid cell rabies vaccine (HDCV, Pasteur-Merieux, Lyon, France), purified Vero cell rabies vaccine (PVRV; Imovax, Pasteur-Merieux, Lyon, France), or purified duck embryo cell rabies vaccine (PDEV; Lyssavac-N, Swiss Serum and Vaccine Institute Berne, Switzerland). Five different anti-rabies immunoglobulins (RIG) are also available, Depending on the treatment centre and financial status of the patient, tissue culture vaccines, rabies immunoglobulins, or both may be recommended for all persons with possible exposure to rabies; for only those who are severely exposed; or for only those who are exposed to animals proven to be rabid. The production cost of the NTV vaccine is P2.48 (US$0.11) per dose. A full course of postexposure treatment with this vaccine consists of 16 doses; 16000 16-dose vials were produced in 1988. All costs related to the administration of this vaccine are borne by the government. Tissue culture vaccines are available only to patients who can afford to purchase them; the retail cost ranges from P417 (US$19.77) per dose for PVRV and P429 (US$20.34) per dose for PDEV to P1200 (US$56.89) per dose for HDCV. The charge for immune globulin for a 50 kg patient ranges from P352 (US$16.69) to P533 (US$25.26) for 1000 units of equine-origin products (ERIG, Berna and ARS, Sclavo) to P6667 (US$316) for 1000 units of human rabies immune globulin (HRIG, Merieux). Other costs associated with rabies postexposure prophylaxis were estimated to total P426 (US$20.20) in private centres; this included physician or hospital fees (about P100 [US$4.74] for the initial cost and P20 [US$0.94) to P30 [US$1.42] for each of four subsequent visits), tetanus antitoxin (P25 [US$1.19]), povidoneiodine and saline for wound cleansing (P18 [US$0.85)

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3 Estimated cost and expensea of 1629 tests to diagnose animal rabies, Republic of the Philippines, 1988

Table

Expense Expense component Transportation Laboratory Supplies Salaries Fee Total

Cost per examination

Public sector

40 79 ~ 90 ~ (57) ~ 112

128691 146610 (92 853) 182448

Private sector

Total

65 160

65 160

92 853 158031

128691 146610 (92 853) 340461

"All expenses in Philippine pesos (average 1988 exchange rate: P21.09 = US$1). ~Cost per examination (weighted average of two facilities). CFigures in parentheses are subtracted from expenses borne by government b e c a u s e t h e y a r e charged to persons having test performed and recouped by the government

and P43 [US$2.04], respectively), and prophylactic antibiotics (P126 [US$5.97] for a 7-day course). In public sector clinics, costs of vaccine administration included that for the needle (P1.5 [US$0.07]), the syringe (P2 [US$0.09]), and the staff salary (P2 [US$0.09]) per visit (5 minutes for the initial interview and 5 minutes for each of 15 subsequent visits, based on staff salary of P60 [US$2.84] per day). The total cost for postexposure treatment was P95.9 (US$4.55) for a course of NTV administered by the government to P14 293 (US$678) for a course of HDCV and human-rabies immune globulin in the private sector (Table 2).

Laboratory diagnosis of animal rabies About 1600 animal brains were examined for rabies in five laboratories in the Philippines in 1988, for an average fee of P57 (US$2.70). If the cost of transporting the specimen to the diagnostic facility (about P40 [US$1.90] per specimen) is included, the total cost of animal rabies diagnostic examinations was about P340 000 (US$16 117), P145 (US$6.87) to P352 (US$16.68) per examination (Table 3). The cost of the equipment, supplies and salaries of the staff performing these tests exceeds the charges since there is a need to make these services available to the general public. The cost of salaries at the diagnostic facilities was P70 (US$3.31) to P242 (US$11.47) per examination, and the cost of supplies and equipment was P75 (US$3.56) to P110 (US$5.21) per examination. The difference in costs between centres is due to fixed costs and a relatively small number of examinations performed at one facility.

Benefits and costs of rabies elimination: D.B. Fishbein e t al.

Cost of epidemiology and research

Cost of eliminating rabies

Animal and h u m a n rabies have not been included in Philippine health statistics since 1985, and there is no formal collation of data at a national level. Costs associated with epidemiology and surveillance are negligible. Although epidemiological studies of human and animal rabies are occasionally conducted by students and epidemiologists, the cost of these investigations is insignificant.

Under the initial assumptions - a dog-to-human ratio of 1:10, 60% vaccination rate, cost per vaccination of either P25 or P90 and discount rate of 8.94% - the cost of an elimination p r o g r a m m e would be P88 (US$4.1) million or P317 (US$15) million. Using the estimate of 295 deaths per year, the cost of preventing one death would be P1.07 million (US$50 700) after the first year, and would fall to P42 983 (US$2038) after 25 years.

Earnings of persons whose death would be prevented

Cost-benefit and sensitivity analysis

The lifetime earnings of Filipinos whose death due to rabies would be prevented as a result of an elimination p r o g r a m m e would be expected to vary with the age and economic status of patients with the disease. Between 1983 and 1986, an average of 295 persons per year died of rabies; 9.2% of the patients were < 4 years of age, 28.6% were between 5 and 14, 32.6% were between 15 and 44, 18.6% between 45 and 64 and 11.0% were older than 65. Based on a per capita income of P12704 in 1988, the combined earning power of persons between the ages of 15 and 44 whose deaths would be prevented through rabies elimination was estimated to be P1.2 (US$0.06) million per year.

When the total annual benefits of elimination are discounted and compared to the costs of the above programmes, both of the initial programmes were favourable economically: the internal rate of return and discount period (time required to recoup the programme costs) under the initial assumptions were 62.1% and 4.1 years, respectively, for the p r o g r a m m e with the lower cost per vaccination and 18.2% and 11.0 years, respectively, for the programme with the higher cost per vaccination. Because there were no precise data on the number of dogs in the Philippines, we performed a sensitivity analysis showing the costs and benefits of rabies elimination over a range of estimates for these components (Table 4). The total p r o g r a m m e costs ranged between P59 (US$2.8), assuming 60% vaccination rate, one dog per 15 humans, and a cost per vaccination of P25 (US$1.19) and P846 (US$40.1), assuming a 60 or 80% vaccination rate, one dog per five humans, and a cost per vaccination of P90 (US$4.26) (Table 4). Using a discount rate of 8.94%, the internal rate of return indicated that the p r o g r a m m e would be advantageous in all cases except in the highest cost programmes, those with the combined assumptions of an extremely large dog population (dog:human ratio of 1:5) and higher cost of vaccination (P90 per dog). With a discount rate of 15% (data not shown), the internal rate of return would be favourable at all but the highest three estimates of p r o g r a m m e cost. The elimination of rabies can also be shown to be economically viable by considering the cumulative net present value of the elimination programmes. Figure I

Total annual benefits of elimination The total costs for rabies control in 1988 were P29.7 (US$1.4) million for canine vaccination, P21.6 (US$1.0) million for postexposure vaccination of humans, and P0.34 (US$0.02) million for animal rabies diagnosis. It should be noted that the Filipino government bore only a small proportion (8.9%, P4.6 [US$0.23 million) of these rabies prevention costs (Tables 1-3). If all these programmes were discontinued, and their cost added to the additional earnings of adults who would have died of rabies, the total economic benefit of rabies elimination would be P52.8 (US$2.5) million 1 year after elimination. The economic benefits of this programme would increase by P1.2 (US$0.06) million each year after elimination because a new cohort of lives would be saved and the earnings of cohorts previously included would recur.

Table 4

Cost-benefit analysis of eliminating rabies in the Republic of the Philippines: sensitivity analysis

Cost of vaccination per dog"

Canines per capita

Dogs vaccinated ~ (%)

Total cost of elimination programme c

Internal rate of return (%)

Discount period (years) °

25 (1.19) 25 (1.19) 25 (1.19) 25 (1.19) 25 (1.19) 25 (1.19) 90 (4.27) 90 (4.27) 90 (4.27) 90 (4.27) '90 (4.27) '90 (4.27)

1:15 1:15 1:10 1:10 1:5 1:5 1:15 1:15 1:10 1:10 1:5 1:5

60 80 60 80 60 80 60 80 60 80 60 80

59 78 88 118 176 235 212 282 317 423 635 846

92.1 69.6 62.1 47.1 32.0 24.4 27.0 20.5 18.2 13.6 8.4 4.4

3.4 3.9 4.1 4.8 6.4 8.2 7.5 9.7 11.0 15.7 >25 Infinite

(2.8) (3.7) (4.2) (5.6) (8.3) (11.1) (10.5) (13.4) (15.0) (20.5) (30.1) (40.1)

aCost in pesos (dollars). ~Percentage of dogs in the Philippines vaccinated during elimination campaign. CMillions of pesos (millions of dollars). ~Years after campaign until costs are recouped, with a discount rate of 8.94%

V a c c i n e , Vol. 9, A u g u s t 1991

585

Benefits and costs of rabies elimination: D.B. Fishbein et al. 600

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Years Figure 1 Cumulative net present value (NPV) of eliminating rabies in the Philippines under four different cost scenarios, m, Dog/human, 1:10, 60% vaccinated, vaccination costs P25, discount rate 8.9%; A, dog/human, 1:5, 80% vaccinated, vaccination cost P25, discount rate 8.9%; [Z, dog/human, 1:10, 60% vaccinated, vaccination cost P90, discount rate 15.0%; X, dog/human, 1:5, 80% vaccinated, vaccination cost P90, discount rate 8.9%

illustrates how varying the number of dogs vaccinated, the cost per vaccination and the discount rate affects the economic benefits of an elimination campaign. DISCUSSION Although our analysis showed that an elimination programme is likely to be economically advantageous, the assumptions made to estimate the costs and benefits of elimination must be critically examined. The ratio of dogs to humans may be greater (or less) than estimated, greatly increasing (or decreasing) the cost of a control programme; better estimates of the canine population should therefore be made before beginning a comprehensive control programme. Because the organization of an elimination p r o g r a m m e has not been agreed upon, it was not possible to determine the actual cost of a nationwide canine vaccination programme. Since agencies and infrastructure responsible for an elimination campaign were not identified, costs related to development of a functional cold chain, recruitment and training of vaccinators, community organization, and transportation for campaign personnel were not estimated and might increase the cost of an elimination campaign beyond our higher cost per dog. However, our cost estimates were based on the cost of ongoing programmes in public and private sectors in the Philippines, programmes that are in place on a limited scale in most islands in the country, and were similar to the estimated costs of elimination programmes in other developing countries 4. Estimated costs should be reviewed at the time of an actual elimination programme. The success of a rabies elimination p r o g r a m m e in the Philippines would be dependent on many factors that are difficult to predict and beyond the scope of this economic study. Political and economic conditions might interfere with the development or implementation of an elimination programme in some areas of the country. If large numbers of stray or community dogs were present and could not be vaccinated in some parts of the Philippines, an elimination p r o g r a m m e based on parenteral vaccination might be unsuccessful in these areas.

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To determine if a change in our assumptions would influence the outcome of our economic analyses, we performed a sensitivity analysis, which showed that all but the most extreme estimates of the cost of an elimination programme would be cost-beneficial when compared with 1988 expenditures for rabies prevention and lost earnings due to human deaths. Moreover, for the sake of caution, estimation of the benefits was kept conservative. For example, we have almost certainly underestimated the number of deaths due to rabies. In addition, we assumed that only 96 of the people whose lives were saved would positively contribute to the economy of the Philippines. We did not include in the analysis the lost earnings of the people who must undergo rabies postexposure prophylaxis or those who develop neurological reactions as a result of this treatment, and made no attempt to place an economic value on the adverse reactions and psychological suffering that would be prevented by eliminating canine rabies. The economic and social value of these benefits must be considered an advantage in eliminating the disease in spite of the cost. Our results show that such an exercise is not really necessary: even with underestimated benefits, rabies elimination appears to be an economically worthwhile project. The financial outlay necessary to eliminate rabies in the Philippines must also be viewed in comparison with the costs and benefits of other health-related expenditures. Since the Filipino government bore only a small proportion of rabies prevention costs (Tables 1. 2 and 3), an elimination programme would be 19 69 times more expensive than 1988 public sector expenditures for rabies prevention. For the government, the cost of a rabies elimination p r o g r a m m e would be substantial in comparison with the costs in 1988 of other health-related expenditures. The 1988 budget for AIDS prevention was about P10 (US$0.5) million, the budget for all communicable disease control activities P200 (US$9.5) million, and that for all health-related activities P4120 (US$195.7) million. When compared with total (private and public sector) expenditures for health care, a one-time expenditure of between P88 (US$4.1) million and P317 (US$15.0) million for rabies elimination would necessitate an expenditure equivalent to 0.8 3.0% of the total (public and private) health care expenditures for a single year (P10629.4 [US$507.0] million). Although a rabies elimination programme might not represent a saving for the government of the Republic of the Philippines, it should not be expected that the government would bear all or even most of the costs of an elimination programme. As with model rabies control programmes in other developing countries 2'15.1(, international funding would probably be available, particularly since, unlike many other countries that have a wildlife reservoir, a one-time expenditure in the Philippines could eliminate all future expenses for this disease. Although it is perhaps unlikely that a nationwide rabies elimination programme would be completed in a single year, a longer programme would probably not affect the conclusions of our analysis. Since most successful canine rabies control programmes have involved short intensive vaccination campaigns, an island-to-island programme would most probably attempt to complete vaccination on an individual island or in a circumscribed geographical area within 1 year 2"3. On each individual island. therefore, the costs and benefits of elimination would be proportional to those presented herein. The islands that

Benef i t s a n d costs o f r a b i e s e l i m i n a t i o n : D.B. F i s h b e i n et al.

make up the country offer other advantages to a nationwide rabies control programme. Compared to non-insular countries, movement of dogs between islands is limited and would make reintroduction of rabies into an area from which it had been eliminated less likely. However, this lack of mobility also makes vaccination campaigns, particularly the movement of personnel trained to organize and conduct these campaigns, more difficult. Unlike countries in the Americas that use members of defence or agriculture departments as a labour force to decrease the cost of vaccination 3, the use of such personnel in the Philippines might not be politically feasible or acceptable since they are sometimes targets of guerrilla groups and therefore not always accepted by the public. Therefore, it is possible that persons would have to be hired and vehicles purchased to successfully carry out nationwide campaigns. Although we did not calculate the cost of hiring personnel and purchasing vehicles for such a programme, the higher of our two vaccination costs per dog was similar to the per animal cost of vaccinating dogs estimated for a national control programme in Tanzania, which included labour and vehicle costs. In addition, the people of the Philippines would need to be convinced of the importance of participating in a nationwide rabies elimination programme. Extensive public education might be necessary to convince the populace to bring their dogs to a central vaccination clinic or to make their dogs available during a door-to-door campaign. For all of these reasons, it remains possible that a programme might be difficult to initiate and even more expensive than we estimated to design, administer and conduct. Our study identified areas where the costs of prevention of both human and animal rabies in the Philippines can be decreased whether or not a national rabies control programme is started. The cost of veterinary vaccines (P20/dose) is high in the Philippines compared with similar products in other developing countries; the use of less expensive vaccines could reduce the cost of the public sector campaign by at least 33%. The cost of human rabies prevention biologicals is also high. While it may be more difficult to reduce the cost of these vaccines, new vaccination regimens, in which small doses of vaccine are administered intradermally, should be investigated~ 7.~8. Similarly, passive immunization with the improved equine rabies immune globulin (ERIG) products that are currently available should be considered ~9'2°. When administration of ERIG is preceded by skin testing to detect hypersensitivity to equine proteins, these products offer equivalent protection with a minimum of adverse reactions. Use of such biologicals is therefore becoming more common in other Asian countries. However, since even the most economical of these regimens is more expensive than those that employ adult nervous-tissue origin vaccine, their use in the Philippines would increase the cost of prevention of human rabies and therefore make elimination more advantageous. Although it is possible that rabies elimination has not been begun in earnest in the Philippines for economic reasons, our analysis shows that such elimination is economically justifiable, In considering rabies prevention strategies, it is important to realize that canine rabies elimination may be more cost-effective than postexposure (or pre-exposure) treatment of humans in preventing the disease 4. In developing countries such as the Philippines,

countrywide elimination of canine rabies may be as costeffective in preventing human deaths as programmes which propose to employ new human vaccines 21'22. Unfortunately, the limited government funds available for health care suggest that funding for such a campaign would have to be obtained from extra-governmental sources. ACKNOWLEDGEMENTS The authors are grateful for the assistance of Mark E. White and Manuel Dayrit of the Field Epidemiology Training Program and Meliadora C. Saniel of the Research Institute for Tropical Medicine, Department of Health, and the Rabies Control Coordinating Council, Manila, in conducting this study. Dr Andrew L. Creese and Patrick J. O'Neill Jr provided valuable advice regarding the economic analysis. Carol Teplis was instrumental in developing the economic model. REFERENCES 1 Turner, G.S. A review of the world epidemiology of rabies. Trans. R. Soc. Trop. Med. Hyg. 1976, 70, 175-178 2 Chomel, B., Chappuis, G., Bullon, F. et al. Mass vaccination campaign against rabies: are dogs correctly protected? The Peruvian experience. Rev. Infect. Dis. 1988,10 (Suppl. 4), $697~$702 3 Belotto, A.J. Organization of mass vaccination for dog rabies in Brazil. Rev. Infect. Dis. 1988, 10 (Suppl. 4), $693~$696 4 B6gel, K. and Meslin, F.-X. Economics of human and canine rabies elimination: guidelines for program orientation. Bull. WHO 1990, 68, 281-291 5 Sasaki, D.M. and Gooch, J.M. Cost effectiveness of Hawaii's anti-rabies quarantine program. Hawaii Med. J. 1983, 42, 157-160 6 Fishbein, D.B., Corboy, J.M. and Sasaki, D.M. Rabies prevention in Hawaii. Hawaii Med. J. 1990, 49, 98-101 7 B6gel, K. and Motschwiller, E. Incidence of rabies and post-exposure treatment in developing countries. Bull. WHO 1986, 64, 883-887 8 Helmick, C.G. The epidemiology of human rabies postexposure prophylaxis, 1980-1981. J. Am. Med. Assoc. 1983, 250, 1990-1996 9 Arambulo, P.N. and Escudero, S.H. Rabies in the Republic of the Philippines: its epidemiology, control, and eradication. J. Philipp. Med. 1971, 47, 2 ~ 2 2 1 10 Beran, G.M. Epidemiological studies and control projects on rabies in the Philippines. In: Rabies (Ed. Nagano, Y.) University Park Press, Baltimore, 1971, pp. 363-369 11 Beran, G.W., Nocete, A.P., Elvina, O. et al. Epidemiological and control studies on rabies in the Philippines. Southeast Asian J. Trop. Med. Public Health 1972, 3, 433-445 12 Steele, J.H. Rabies in the Americas and remarks on global aspects. Rev. Infect. Dis. 1988, 18 (Suppl. 4), $585-$597 13 Escobar Cifuentes, E. Program for the elimination of urban rabies in Latin America. Rev. Infect. Dis. 1988, 10 (Suppl. 4), $689-$692 14 Bureau of Statistics of the International Monetary Fund. Philippines. In: International Financial Statistics Yearbook International Monetary Fund, Washington, 1989, pp. 582-585 15 Ben Osman, F. and Haddad, N. Experience in field rabies control programs. Rev. Infect. Dis. 1988, 10 (Suppl. 4), $703-$706 16 Beran, G.W. and Frith, M. Domestic animal rabies control: an overview. Rev. Infect. Dis. 1988, 10 (Suppl. 4), $672-$677 17 Warrell, M.J., Suntharasamai, P., Nicholson, K.G. et al. Multi-site intradermal and multi-site subcutaneous rabies vaccination: improved economical regimens. Lancet 1984, i, 874~876 18 Chutivongse, S., Wilde, H., Supich, C., Baer, G.M. and Fishbein, D.B. Postexposure prophylaxis for rabies with antiserum and intradermal vaccination. Lancet 1990, 335, 896~98 19 Wilde, H., Chomchey, P., Prakongsri, S. and Punyaratabandhu, P. Safety of equine rabies immune globulin [letter]. Lancet 1987, ii, 1275 20 Wilde, H., Chomchey, P., Prakongsri, S., Punyaratabandhu, P. and Chutivongse, S. Adverse effects of equine rabies immune globulin. Vaccine 1989, 7, 10-11 21 Creese, A.L. Cost effectiveness of potential immunization interventions against diarrhoeal disease. Soc. Sci. Med. 1986, 23, 231240 22 Institute of Medicine. Diseases of Importance in Developing Countries Vol. 2. National Academy Press, Washington, 1986, p. 432 Vaccine, Vol. 9, A u g u s t 1991

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