Epidemiology of Taenia Solium Taeniasis/cysticercosis in India and Nepal

The fact that cysticercosis is a major health hazard in India and Nepal is evident from the large number of patients with neurocysticercosis (NCC) managed in hospitals in the two countries in recent years. Unfortunately, population-based epidemiological data on Taenia solium taeniasis and cysticercosis are lacking from both countries. Hospital-based data and small population-based studies form the basis of this report. India: cysticercosis is prevalent in virtually all states of India, the only possible exceptions being Kerala, and Jammu and Kashmir. It is generally believed that the disease is more prevalent in north than south India. NCC accounts for anywhere between 8.7-50% of patients presenting with recent onset of seizure. The peculiarity of the disease in India is the high incidence of patients with the solitary form of the disease, namely solitary cysticercus granuloma (SCG). About 60-70% of all Indian patients with NCC have a SCG. The reasons for the high incidence of SCG vis-à-vis the multilesional form of the NCC (MNCC) are unclear, but may be linked to the low parasite load in the community. The prevalence of taeniasis has been reported to be between 0.5-2%. However, a recent study in a pig-rearing community from the northern state of Uttar Pradesh reported that 17 of 72 (38%) members of that community had evidence of taeniasis. The prevalence of taeniasis is probably higher in northern than southern India. The prevalence of porcine cysticercosis has been studied in pig carcasses in slaughterhouses of north and east India and ranges from 7-12% although a recent study from the pig-rearing community in Uttar Pradesh placed the figure at 26%. Nepal: even hospital-based data on cysticercosis is lacking from Nepal because of the lack of access to CT scanners for the vast majority of patients. However, several patients from Nepal seek treatment in Indian hospitals and there have been reports of NCC in several Nepalese patients from Indian and other foreign hospitals. Recently, a study of taeniasis in certain ethnic groups of Nepal revealed a prevalence of 10-50%. Porcine cysticercosis rates were estimated to be 14 and 32% by examination of carcasses and lingual palpation of live pigs, respectively. It is evident from the data presented that cysticercosis is a major public health problem in both countries. Epidemiological data to estimate the magnitude of the problem has to be gathered. These data will help in getting the disease on the public health agenda of both countries. Steps towards control and possible eradication of the disease are needed, as the disease causes not only chronic morbidity, but also contributes to economic losses in an already impoverished population. Unfortunately, the disease did not receive the attention due to it in India, and it did not gain prominence as a major cause of neurological morbidity and economic loss. However, only over the last two decades has there been interest in the disease in India and more recently in Nepal. Consequently, there is little epidemiological data on the disease in both countries. Data on the prevalence of taeniasis, human cysticercosis, and porcine cysticercosis in India and Nepal are sparse and are based on hospital-based studies or small community-based investigations. MATERIALS AND METHODS Data acquisition The following tools were employed to obtain the epidemiological data on T solium taeniasis and cysticercosis in India and Nepal: 1) Medline search using the search words “cysticercosis” and “India” and “Nepal”; and 2) Personal knowledge of published articles on the disease from India and Nepal. Correspondence: Vedantam Rajshekhar, Department of Neurological Sciences, Christian Medical College Hospital, Vellore 632004, India. Fax: 091-416-2232103/2232035 E-mail: [email protected] INTRODUCTION Taenia solium taeniasis and cysticercosis are diseases associated with poverty, pork consumption, and poor pig husbandry practices. It is, therefore, not surprising that the prevalence of the disease is high in India and Nepal, both of which are developing countries with large populations below the poverty line. The disease has been known to exist in India for several hundreds of years. A seminal paper on the subject was published by Dixon and Lipscomb in 1961. They carefully studied the disease in 450 British soldiers who served in India, and clarified the latency and other features of the disease in this group of patients. SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH 248 Vol 35 (Suppl 1) 2004 Data presentation The epidemiological data are presented under the following categories: hospital-based data on human cysticercosis; community-based data on human cysticercosis; communityor hospital-based data on taeniasis; data on porcine cysticercosis. RESULTS AND DISCUSSION The above data are summarized in Table 1. Geographic and demographic profile Since economic conditions and dietary practices impact directly on the transmission of the disease, knowledge of these features is helpful in understanding the disease dynamics in a given population. It might, therefore, be relevant to discuss briefly the geography and demographics of the populations of India and Nepal before embarking on a discussion of the epidemiology of cysticercosis and taeniasis. India. India is a subcontinent with a population of over a billion people. The climate is mainly tropical. A vast majority of the population (80%) profess the Hindu religion but this religion is varied in its beliefs and practices in different regions of the country and also between different castes in the same region. Consumption of beef (cow meat) is prohibited by the Hindu religion and although consumption of pork is not prohibited, its consumption is generally restricted to the lower castes. Muslims constitute 14% of the population and they do not consume pork. Sikhs, Jains, Buddhists, and Christians constitute the rest of the population and have differing dietary practices. About 20-30% of the population is strictly vegetarian, but of the rest, only a minority eat meat products on a daily basis. According to a recent World Bank estimate, 29% of the population lives below the poverty line. The literacy rates average about 60%. Toilet facilities are mostly limited to populations in the urban regions (30%) and it is estimated that only a quarter of the population has access to proper, hygienic toilets. The government provides free healthcare to all, but the facilities in most government hospitals are limited. Some states, such as Tamil Nadu, however, subsidise access to high technology investigations such as CT scanning and have provided CT scan facilities in all district general hospitals. The private healthcare sector is large and provides high quality healthcare, although at a cost. Consequently, almost all major towns in India have one if not more CT scanners (about >800 in all). Nepal. Nepal is a mountainous country bordering India to the north, with tropical and temperate climates. It has a population of 23 million. The population is predominantly Hindu (>95%). Pork consumption is restricted to the lower castes but recently more members of the upper castes are also eating pork. Beef (buffalo meat) is consumed by several people. Nearly 42% of the population lives below the poverty line and literacy rates average 42%. Toilet facilities are available to less than a third of the population. There are few CT or MR facilities in the country, and these are restricted mainly to the capital region of Kathmandu. Hospital-based data on human cysticercosis Although there are several publications on cysticercosis in humans from India, such publications are lacking from Nepal. India. There are several publications, from India, on the clinical aspects of neurocysticercosis (NCC) and ocular cysticercosis. This is ample evidence for the widespread occurrence of the disease in India. The disease is prevalent in virtually all states of the country, although the prevalence rates vary significantly between different states (Rajshekhar and Chandy, 2000). There are few reports of patients with cysticercosis from Jammu and Kashmir, a predominantly Muslim state, and Kerala, where educational levels and hygiene standards are probably the highest in the country (Singh et al, 2002). Table 1 Prevalence data on Taenia solium taeniasis and cysticercosis in India and Nepal. Country Human cysticercosis Taeniasis Porcine cysticercosis India NA 2-38% 7-26% Nepal NA 10-50% 14-32% See text for details on methodologies used to arrive at the prevalence data; NA, not available.