Brucellosis

In Mongolia and central Asian countries after democratic reform and the shift from dependence on the former Soviet Union in 1990, human brucellosis reemerged as a major, but preventable, disease (9). After consultations with experts, the World Health Organization (WHO) raised the question whether mass vaccinations of animals saved money for the public health sector. We used an animal-to-human transmission model to estimate the economic benefit, cost-effectiveness, and distribution of benefit (to society and the public health and agricultural sectors) of mass brucellosis vaccination of cattle and small ruminants (10). The intervention consisted of a planned 10-year annual livestock mass vaccination campaign using Brucella melitensis Rev-1 for small ruminants and Brucella abortus S19 for cattle. In a scenario of achieving 52% reduction of brucellosis transmission between animals, 51,856 human brucellosis cases could be averted, which would add up to a gain of 49,027 human disability-adjusted life years (DALYs; see Appendix). The human death rate from brucellosis is considered to be <2% (11) and was not assessed in this study (4). Estimated intervention costs were US $8.3 million, and the overall benefit was US $26.6 million (Table 1). This results in a present net value of $18.3 million and a benefit-to-cost ratio for society of 3.2 (95% confidence interval [CI] 2.27–4.37). If the costs of the intervention were shared between the sectors in proportion to the benefit to each, the public health sector would contribute 11%, with a cost-effectiveness ratio of $18 per case averted. However this ratio does not account for illness imposed by brucellosis. When the number of DALYs averted is assumed to be 49,027, the cost-effectiveness ratio is $19.1 per DALY averted (95% CI 5.3–486.8). If costs of vaccinating livestock are allocated proportionally to all benefits, the intervention is cost-saving and cost-effective for the agricultural and the public health sectors (4). With such an allocation of costs to benefits per sector, brucellosis control becomes one of the most cost-effective interventions (<$25 per DALY gained) in the public health sector, comparable to cost-effectiveness of vaccinating women and children or treating tuberculosis.

Rabies

Most human deaths from rabies occur in tropical resource-limited countries (12). In Africa and Asia, an estimated 24,000–70,000 persons die of rabies each year (13). The domestic dog is the main source of exposure and vector for human rabies (14). Rabies in humans can be prevented by appropriate postexposure prophylaxis, which is not, however, always available and affordable in resource-limited countries. Human rabies can also be prevented through vaccination of the animal vector. Again, particularly for countries with limited resources, we must ask whether it is cost-saving to the public health sector to prevent human rabies by vaccinating dogs. Bögel and Meslin showed that over 15 years in areas where the virus still circulates in the dog population, dog vaccination combined with postexposure treatment of dog-bite patients is more cost-effective than postexposure prophylaxis alone (15). However, in many countries, little is known about the real cost of mass vaccination of dogs, and quantitative data are urgently needed to evaluate the cost-effectiveness of different rabies control strategies in resource-limited countries; rabies control strategies in developing countries are currently under review by WHO (F. Meslin, pers. comm.).

We performed a cost analysis of a pilot dog rabies vaccination campaign in which 3,000 dogs in N’Djaména, Chad, were vaccinated (16). The average cost per dog was US $2.14 to the public sector (for vaccine and logistics) and $0.97 to the private-sector dog owner, which brings the full cost to society to $3.11. If all 23,600 dogs in N'Djamena were vaccinated, the average cost per dog would fall to $1.48 for the public sector and $2.45 for society (Table 2). Private sector costs account for 31% of the cost to vaccinate 3,000 dogs and 40% of the cost to vaccinate 23,600 dogs (17). The above costs per vaccinated dog tally with the estimates by Bögel and Meslin (15). The cost estimates provided account for only 1 year of vaccination. In the year before this campaign (16,17), 69 persons were reported to have been exposed to 29 rabid dogs. If one assumes that human exposure could be avoided by mass vaccination of dogs, the cost-effectiveness of mass dog rabies vaccination would be $837 per averted human exposure ($57,774 per 69 averted exposures). If one assumes that about 16% of the exposed persons would actually become ill with rabies and die (18), the cost-effectiveness would be $57,774 per 11 averted deaths ($5,252 per averted death). But if we consider that reported human rabies cases in Africa underestimate the true number of human rabies cases by a factor of 10 to 100 (18), then the cost-effectiveness would be $52–$525 per averted death. Hence, mass vaccination of dogs is a comparatively inexpensive and ethical way to control the disease in animals and to prevent human exposure and illness, especially in resource-limited countries. More research is needed to assess the dynamics of dog-to-human rabies transmission and the frequency of revaccination programs needed because of turnover in dog populations and continued risk for reintroduction of rabies from outside sources to unvaccinated dogs.

Avian Influenza

The spread of highly pathogenic avian influenza is a global threat to all countries that have a poultry industry, semicommercial poultry production, or backyard poultry operations and has already caused enormous economic losses (19). Moreover, the risk for human pandemic influenza originating from highly pathogenic avian influenza in conjunction with human influenza A virus is very high, with an estimate of >100,000 deaths for the United States alone (20). To implement disease prevention and control measures, early identification of emerging patterns of disease is necessary and uses economic methods to determine which mix of measures is most cost-effective. Resource-limited countries in Africa are almost devoid of surveillance capacity and efficient early warning systems, which would be crucial. Surveillance of cross-border diseases cannot be restricted to countries that have the funds. High-income countries would ultimately benefit by providing funding for surveillance and control to low-income countries. Comprehensive economic assessment of this issue are, however, lacking so far.