Epidemiology of blindness in Nepal.

This report presents the major findings of the Nepal Blindness Survey, the first nationwide epidemiological survey of blindness, which was conducted in 1979-80. The survey was designed to gather data that could be used to estimate the prevalence and causes of blindness in the country. Ancillary studies were conducted to obtain information on socioeconomic correlates and other risk factors of blinding conditions and patterns of health care utilization.The nationwide blindness prevalence rate is 0.84%. Cataract is the leading cause of blindness, accounting for over 80% of all avoidable blindness. Trachoma is the most prevalent blinding condition, affecting 6.5% of the population. Very few cases of childhood blindness were detected.The implications of the survey findings for programme planning, health manpower development, and health education are discussed.

Associations among cataract prevalence, sunlight hours, and altitude in the Himalayas.

The relationship between cataract prevalence, altitude, and sunlight hours was investigated in a large national probability sample survey of 105 sites in the Himalayan kingdom of Nepal, December 1980 through April 1981. Cataract of senile or unknown etiology was diagnosed by ophthalmologists in 873 of 30,565 full-time life-long residents of survey sites. Simultaneously, the altitude of sites was measured using a standard mountain altimeter. Seasonally adjusted average daily duration of sunlight exposure for each site was calculated by a method which took into account latitude and obstructions along the skyline. Age- and sex-standardized cataract prevalence was 2.7 times higher in sites at an altitude of 185 meters or less than in sites over 1000 meters. Cataract prevalence was negatively correlated with altitude (r = -0.533, p less than 0.0001). However, a positive correlation between cataract prevalence and sunlight was observed (r = 0.563, p less than 0.0001). Sites with an average of 12 hours of sunlight exposure had 3.8 times as much cataract as sites with an average of only seven hours of exposure. Sunlight was blocked from reaching certain high altitude sites by tall neighboring mountains.

Reliability of ophthalmic diagnoses in an epidemiologic survey.

In the Nepal Blindness Survey, 39,887 people in 105 sites were examined by 10 ophthalmologists from Nepal and four other countries during 1981. Ophthalmic protocols were pretested on approximately 3000 subjects; however, interobserver variability was inevitable. To quantify the amount of variability and assess the reliability of important ophthalmic measures, a study of interobserver agreement was conducted. Five ophthalmologists, randomly assigned to one of two examining stations in a single survey site, carried out 529 pairs of examinations. Eighty demographic and ophthalmic variables were assessed at each station. In 62 of 80 (77.5%) measures, observer agreement exceeded 90%. Since pathologic findings were rare, however, chance agreement alone could yield misleadingly high per cent agreement; therefore, the kappa statistic was used for assessing comparative reliability of ophthalmic measures. There were 74 measures for which kappa could be computed and ranked by strength of agreement: 20 (27%) showed excellent agreement (kappa = 0.75-1.00), 39 (53%) showed fair to good agreement (kappa = 0.40-0.74), and 15 (20%) showed poor agreement (kappa less than 0.40). In general, measures dealing with blindness prevalence or causes of blindness showed substantial or almost perfect agreement, while polychotomous descriptions of rare clinical signs demonstrated less agreement.

Testing for polychlorinated biphenyls in human milk.

Reports of polychlorinated biphenyl (PCB) contamination of human milk have raised questions about the possible risks of breast-feeding and whether nursing mothers ought to have their breast milk tested. Current data on contamination of human milk are needed so that pediatricians can make informed recommendations about breast milk testing and breast-feeding. With consideration of recent findings of PCB contamination of human milk in Michigan, recommendations concerning breast milk testing and breast-feeding are made. No major changes in current breast-feeding practices are advised. However, breast milk testing is recommended for certain nursing mothers who have had potentially high exposure to PCBs. Limiting the duration of breast-feeding may also be advisable for mothers with high PCB milk fat levels in order to reduce infant exposure to PCBs.

Polychlorinated biphenyl contamination of nursing mothers' milk in Michigan.

The problem of environmental contamination by toxic substances and human exposure to these substances has attracted increased attention in recent years. Particular concern has centered on polychlorinated biphenyls (PCBs), which have become widespread environmental pollutants as well as contaminants of the human population. This paper reports data from a study of PCB contamination of nursing mothers' breast milk in Michigan. During 1977 and 1978, breast milk samples of 1,057 nursing mothers residing in Michigan were tested for PCB residues. All of the 1,057 samples collected from 68 of the state's 83 counties contained PCB residues ranging from trace amounts to 5,100 parts per million (fat weight basis). The mean level was 1,496 parts per million (ppm), with 49.5 per cent of the samples having PCB levels of 1-2 ppm, 17.4 per cent had 2-3 ppm, and 6.14 per cent had more than 3 ppm. There was no consistent trend in the level of PCB contamination over the 24 months of monitoring. The mean PCB level for the eighth quarter of monitoring was slightly higher than for the first quarter. The public health significance of PCB contamination in human populations and its effects on breast-fed for eight months by a woman with the average PCB level in this sample would have an estimated body burden of approximately 0.89 ppm of PCBs. The implications of PCB contamination of human milk with regard to current breast-feeding practices are discussed and several precautionary measures are recommended.

Occupationally-acquired smallpox in an IgM-deficient health worker.

A 21-year-old Indian who worked as a vaccinator in the smallpox programme developed an atypical case of variola major despite several previous, successful vaccinations. The clinical course of the disease was unusual, as there were two distinctly separate "crops" of smallpox. The disease began less than one month after a successful vaccination, which therefore gave the briefest period of protection recorded for this reliable immunization. The patient was found to have a virtually complete IgM deficiency with normal levels of circulating antibody against orthopox virus.

Is the diagnosis of "mass hysteria" an excuse for incomplete investigation of low-level environmental contamination?

"Mass hysteria" is an epidemic diagnostic term used to characterize unexplained outbreaks of syncope among women. A syncope outbreak among women in a meeting in a rural area of Michigan prompted an intense investigation for etiology. Low levels of ozone; carbon monoxide, and pentane were found associated with the outbreak. These levels were too low by themselves to explain the symptoms. A sociometric scale of intensity of illness was devised and found to be highly correlated (r = -0.94) with the weight of those who fainted. It is argued that mass hysteria may be the result of interactions of low levels of toxicants and may not be a result of the "hysterical" behavior in women at all.

Breast-milk monitoring to measure Michigan's contamination with polybrominated biphenyls.

In 1973 and 1974, several thousand Michigan dairy farms were contaminated by polybrominated biphenyls (P.B.B.) as the result of an industrial accident. An unknown quantity of contaminated meat and dairy products entered the food chain before contaminated farms were quarantined. To determine the extent of human exposure, P.B.B. concentrations were measured in human breast milk, which was collected in a random-sample survey from nursing mothers throughout Michigan. 96% of 53 samples from Michigan's lower peninsula and 43% of 42 samples from the less densely populated upper peninsula contained detectable levels of P.B.B. These data indicate that about 8 million of Michigan's 9.1 million residents have detectable body burdens of P.B.B.

Certification of smallpox eradication.

The world's last known case of smallpox resulting from human-to-human transmission in an endemic focus occurred in Somalia in October 1977, and there remains the task of documenting the global eradication of the disease and establishing the safety of vaccination. Those countries as yet uncertified have been grouped into four categories according to the procedures recommended for their certification. An important criterion for deciding the type of procedure is how recently smallpox was endemic in a particular country. This paper is concerned with those countries in which the disease has been nonendemic for some years but which have not yet received certification of eradication. One such country is Burma, which was certified free of smallpox in 1977, some 8 years after its last reported case but 2 years after the last case in Bangladesh, with which it shares a long frontier. The procedures used in Burma and the lessons that were learnt therefrom are described.