Risk factors associated with leptospirosis in northeastern Thailand, 1998.

Leptospirosis is a zoonotic disease of worldwide distribution caused by spirochetes of the genus Leptospira. Humans are infected through direct contact with infected animals or through exposure to fresh water or soil contaminated by infected animal urine. Leptospirosis is characterized by acute fever that can be followed by a more severe, sometimes fatal illness that may include jaundice and renal failure (Weil's disease), meningitis, myocarditis, hemorrhagic pneumonitis, or hemodynamic collapse. To identify potential risk factors for leptospirosis in Thailand, we conducted a matched case-control study in Nakornratchasrima Province of the northeastern region. Fifty-nine cases and 118 controls were included in the study. Four activities in the two weeks prior to illness were independently associated with leptospirosis infection: walking through water (odds ratio [OR] = 4.9, 95% confidence interval [CI] = 1.7-14.1), applying fertilizer in wet fields for more than 6 hr a day (OR = 3.4, 95% CI = 1.5-7.8), plowing in wet fields for more than 6 hr a day (OR = 3.5, 95% CI = 1.1-11.6), and pulling out rice plant sprouts in wet fields for more than 6 hr a day (OR = 3.1, 95% CI = 1.02-9.3). Identification of these risk factors on admission might prove useful for early diagnosis and treatment of leptospirosis in Thailand.

Progress and achievement of rabies control in Thailand.

The breakthrough in production of highly efficacious human and animal rabies vaccines has led to successful rabies control in developed countries, but rabies is still a major health problem in many developing countries. In Thailand, the new cell culture vaccines-purified chick embryo cell (PCEC), purified Vero cell (PVRV), purified duck embryo (PDEV) and human diploid cell (HDCV) are available, and since 1993 have completely replaced the nervous tissue vaccines. The impact of these cell culture vaccines has been considerable, with the number of human rabies deaths decreasing from 200-300 in the early 1980s to 74 in 1995. Rabies prevention has also focused on the vaccination of dogs, and since 1992, the year the Rabies Prevention Act was announced, every owned dog has to be vaccinated at 2-4 months of age annually thereafter. However, only about 20% of dogs have been vaccinated. In 1995, the Ministry of Agriculture and Cooperation collaborated with the Ministry of Public Health to set up a target of no human rabies deaths in 1996, and a rabies-free Thailand by the year 2000. An extensive educational campaign is underway.

Rabies in Thailand: 1990.

Of the more than 100,000 courses of postexposure rabies treatment given in Thailand annually, 95% consist of brain tissue-derived vaccine without immune globulin. Rabies tissue culture vaccines and immune globulins are expensive by the standards of developing countries. When they are given according to either of two proven intradermal postexposure schedules, significant savings can be achieved without loss of efficacy. Purified equine rabies immune globulins account for approximately 10% of the cost of human products administered to exposed individuals and have been shown to be safe and effective. A canine preexposure immunogenicity study with a potent, inactivated tissue culture vaccine revealed that 12.5% of Thai dogs failed to develop protective antibody titers 2 months after one subcutaneous injection. Previous studies have shown significant antigenic differences between Thai street rabies virus and European and North African strains.

Failure of rabies postexposure treatment in Thailand.

Three failures of postexposure rabies treatment using imported purified duck embryo cell and Vero cell rabies vaccines are reported from Thailand. Reference is made to eight additional previously reported Thai patients, six of whom had received human diploid cell vaccine. An analysis of these cases reveals that there were serious flaws in management in all of these patients. It is stressed that 45% of human rabies deaths in Thailand occur within 20 days of being bitten and 71% are dead within 28 days. This short incubation period does not allow much time to start immunotherapy. Of Bangkok dogs found to have rabies at autopsy, approximately 8% have a rabies immunization history. Once a dog has bitten a patient immunotherapy should not be delayed in countries with a high incidence of dog rabies. Patients with chronic disease, alcoholics and drug addicts may have an impaired immune response to postexposure rabies vaccines.

A high incidence of neurological complications following Semple anti-rabies vaccine.

A study was conducted to determine the incidence of neurological complications among a cohort of 6,980 recipients of Semple vaccine administered in Bangkok and 5 nearby provinces in 1984. A review of all patients admitted to public hospitals in these 6 provinces discovered a total of 32 cases, with neurological complications following Semple vaccine. Twenty-two cases (68.8%) were encephalitis or myelitis. The complication rate was 3.6 times higher for males than females and the rate was lowest in the 0-14 year age group. Vaccinees receiving large daily dose of vaccine had a higher rate of complications than those with low dose regimen. One patient died, giving the case-fatality rate of 3.13 per cent. Since the search was limited, the rate of neurological complications to Semple vaccine was a minimum of 4.6 cases per 1,000 vaccinees [1:220]. This complication rate was much higher than most rates reported previously. It is imperative to find economically feasible alternatives to Semple vaccine.