Animal Bites and Rabies: Situation in Iran

M. Zeynali DVM, MPH,* A. Fayaz DVM, PhD,** A. Nadim MD, PhD***

*Department General of Disease Control, Ministry of Health and Medical Education, **Pasteur Institute of Iran, ***Institute of Public Health Research, Tehran, Iran

Key Words · Rabies · animal bites · epidemiology.

Introduction

Animal bite is a major public health problem not only for the associated risk of acquiring secondary infections including those by C. tetani, C. perfringens and occasional death due to trauma (which occurs often in children) but also for the possibility of contracting rabies which, if left unrecognized and untreated, is almost invariably fatal.

In the countries of the Eastern Mediterranean Region of the World Health Organization (WHO), rabies has been recognized as an important health problem.¹ Tourists visiting these countries are strongly advised to undergo pre-exposure vaccination. According to WHO reports, the following figures represent the number of human deaths due to rabies in these countries in 1995 (Table 1). Pakistan, though not listed in Table 1, is recognized as having the largest number of cases of human rabies in the region.²

Rabies is endemic in the wildlife population in Iran where the infection of domestic livestock is frequent.³ As a consequence, management of this problem is one of the most important priorities of the Iran Health Ministry.

Rabies has a special place in the history of medical research in this country.⁴ Historically, in 1919, an Iranian delegation, dispatched in the peace treaty after World War I, visited the Pasteur Institute in Paris and made arrangements for the establishment of the Pasteur Institute for rabies prophylaxis in Iran. They first started to make rabies vaccines using the spinal cords of rabbits, however, these vaccines were later changed to the formal phenol-treated vaccines using the spinal cords of lambs a process which is currently utilized in many parts of the world. Thereafter, many research studies of international importance on rabies were carried out in Iran^4,5, including the first successful field trial on the use of serum for post-exposure prophylaxis.⁴

Materials and Methods

All the provincial health centers in Iran were asked to complete a questionnaire for each case of animal bite referred to health centers or hospitals (public or private) in their region during the years 1996-1998. These questionnaires contained questions regarding the rabid animal, the results of laboratory examination of specimens, age, gender, occupation of patients, and method of vaccination (complete or incomplete) of the victims. The results of the tests on animal specimens were obtained from the Pasteur Institute of Iran.

Results

The total number of exposed persons to animal bites has increased from 57,070 in 1996, 59,481 in 1997 and 65,632 in 1998. Table 2 shows the species of rabid animals, and the type of vaccination regimen adopted. Figure 1 shows the incidence of animal bites in various parts of the country. The average incidence for the whole country was 95 per 100,000 population. Bites were frequent among the age group of 10-29 years (Table 3). Most of the cases were farmers, and housewives (Table 4), the majority of whom had been wounded on their feet or hands (Table 5).

In 1996, around 85% of cases were bitten by dogs (86% in 1997), 4% by cats (same as 1997), and 11% by other animals (9.7% in 1997).

Most of the positive animal samples in 1996 (Table 6) and 1997 were from cows. In 1997, 480 out of 719 suspected cases of animal rabies, were found positive for the disease. All 25 samples of rats were negative and it appears that this animal plays no role in rabies transmission. Figure 2 shows the geographical distribution of positive animals for rabies in different provinces of the country.

There were 8 fatalities due to rabies; 4 students, 2 farmers, and 2 shepherds. Seven cases of this group, were 10-19 years of age. [Figure 3]

Animal bites were more common in summer than in winter. The difference, however, was not statistically significant.

Discussion

Any warm-blooded animal can be infected by rabies virus, albeit with different susceptibilities. Dog bites are responsible for about 80% of animal bite wounds. Foxes and other wild carnivores are also highly susceptible to rabies, while man, domestic dogs and herbivores are less vulnerable.⁶ In the majority of cases, the cause of rabies in humans is dog bites, however, fox and wolf bites have also been reported to convey rabies.

In the United States, bite wounds account for approximately 1% of all emergency room visits.⁷ Of an estimated 1 to 2 million bite wounds, nearly 80% cause only minor injuries and the victims do not seek medical attention.⁷

The results of this study underlines the importance of animal bites and rabies in Iran. Rabies vaccination is frequently used in Iran and imposes a heavy financial burden on the country's economy. In Iran, the number of reported animal bites has increased dramatically from 66,370 in 1987 to 183,000 in 1997. The increase might in part be due to the improved reporting system due to the expansion of health centers to almost all rural areas. The increasing number of stray dogs in different provinces of Iran has raised the number of exposed persons nationwide. A total of 57,070 exposed individuals in 1996, 59,481 in 1997, and 65,632 in 1998, received vero rabies post-exposure vaccine. In 1996, around 10,000 cases received a complete 5-injection course of vaccination, and 47,000 received the incomplete 3-injection course.

In previous years, almost all cases of rabies- related fatalities were due to dog bites (17 deaths in 1992), but in 1996, 3 of 8 cases who died of rabies suffered from fox bites. Most of these fatalities were primarily due to late referral to health centers.

Although the number of animal bites in our country is increasing,² this rise is commensurate with the population growth rather than a genuine rise in prevalence.

The species of animals most likely to be infected with rabies vary from region to region. In the Caspian littoral , jackals and stray dogs are the most important rabid animals, while, in the mountainous areas of the central plateau, foxes and wolves play a more important role.¹ Overall, most cases of human rabies in Iran are caused by dog bites.

Epizooties of rabies are cyclical so that on spot maps of the distribution of animal rabies, the annual variations clearly indicate

that epizootes migrate from place to place. Therefore, the distribution pattern reported in this study period differs from those reported previously.¹

The results of this study reflect the potential dangers of animal bite and risks of contracting rabies in Iran concluding that the different aspects of the disease should be highlighted in health education activities.

Acknowledgements

We are indebted to all the staff of the provincial Health Centers who helped us to collect information at a national level. We would also like to thank the staff of the Division of Rabies at the Pasteur Institute of Iran who provided us with information on testing animal samples for rabies.

References

1 Information Circular, WHO Mediterranean Zoonoses Control Center. 1996; No 40-April.

2 WHO-EMC. 200 World Survey of Rabies. 1996; No 31.

3 Benenson A. Control of Communicable Disease Manual. 6th ed. APHA 1995:382-90.

4 Bahmanyar M, Fayaz A, Nour-Salehi S, et al. Successful protection of human exposed to rabies infection. Post-exposure treatment with the new human diploid cell rabies vaccine and antirabies serum. JAMA 1976; 236(24):2751-4.

5 Kuwert EK, Marcus I, Werner J, et al. Some experiences with human diploid cell strain-(HDCS) rabies vaccine in pre- and post-exposure vaccinated humans. Dev Biol Stand 1978;40:79-88.

6 Warrell DA. Rhabdoviruses: rabies and rabies related viruses. In: Weatheral DJ, Ledingham JGG, Warrell DA. Oxford Textbook of Medicine. 2nd ed. Oxford: Oxford Medical Publication. 1986.

7 Goldstein EJC. Bite wounds and infection. Clin Infect Dis 1992;14:633.

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