Marcelo E. Cruz

Neurocysticercosis is an infection of the nervous system caused by Taenia solium. It is the most important human parasitic neurological disease and a common cause of epilepsy in Africa, Asia, and Latin America, representing enormous costs for anticonvulsants, medical resources and lost production. Neurocysticercosis is a human-to-human infection, acquired by the faecal-enteric route from carriers of intestinal T. solium, most often in areas with deficient sanitation. Intestinal tapeworms cause few symptoms, but adult taeniae carried by humans release large numbers of infective eggs and are extremely contagious. Ingestion of poorly cooked pig meat infested with T. solium larvae results in intestinal taeniosis but not neurocysticercosis. With a view to hastening the control of taeniosis and neurocysticercosis we propose that neurocysticercosis be declared an international reportable disease. New cases of neurocysticercosis should be reported by physicians or hospital administrators to their health ministries. An epidemiological intervention could then be launched to interrupt the chain of transmission by: (1) searching for, treating and reporting the sources of contagion, i.e. human carriers of tapeworms; (2) identifying and treating other exposed contacts; (3) providing health education on parasite transmission and improvement of hygiene and sanitary conditions; and (4) enforcing meat inspection policies and limiting the animal reservoir by treatment of pigs. We believe that the first step required to solve the problem of neurocysticercosis is to implement appropriate surveillance mechanisms under the responsibility of ministries of health. Compulsory notification also has the major advantage of providing accurate quantification of the incidence and prevalence of neurocysticercosis at regional level, thus permitting the rational use of resources in eradication campaigns.

Taeniasis and cysticercosis are, respectively, infections with the adult and larval stages of tapeworm parasites belonging to the genus Taenia. The World Health Organization (WHO) estimates that Taenia infections afflict approximately 50 million people annually and kill 50,000. One may assume all of these deaths to be the result of T. solium neurocysticercosis. Taenia infections also lead to the death of many cattle and swine, and resulting substantial economic losses. Swine and cattle serve as the intermediate hosts for the larval stage tapeworm parasites, while humans are the obligatory final stage hosts. Humans become infected with Taenia by ingesting raw or inadequately cooked meat of infected intermediate hosts. Mature tapeworms then produce eggs in the human hosts which are excreted and eventually consumed by animal hosts. The prevalence of Taenia is highest in the rural areas of Latin American, Asia, and Africa, but the parasites are vulnerable to eradication. More success has been had in thwarting the spread of T. solium than T. saginata. Sections briefly discuss the biology and transmission of Taenia; the medical and veterinary impacts; prevalence and distribution; the case for eradication; current strategies; remaining barriers; news tools and knowledge; and research and planning needs. Current strategies include long- and short-term interventions developed by the WHO and the Pan American Health Organization based upon the mass treatment of taeniasis in existing transmission foci.

BACKGROUND: Taenia solium neurocysticercosis (NCC) has been documented as one of the major causes of epilepsy in developing countries. However, methodological limitations have hindered the evaluation of the epidemiological relationship between cysticercosis and epilepsy at the community level. METHODS: We used the WHO protocol for epidemiological evaluation of neurological disorders to conduct a door-to-door survey among 2723 residents of San Pablo del Lago, an Ecuadorean rural community in which T. solium taeniasis/cysticercosis was known to be endemic. The WHO protocol was complemented by neuroimaging and immunological tests to confirm the diagnosis of this infection. RESULTS: In all 31 people suffering from active epilepsy were detected (prevalence 11.4 per 1000, 95% CI:7.7-15.4); 26 agreed to undergo a computer tomography (CT) examination, and 28 agreed to have blood drawn for serodiagnosis. Fourteen of the 26 (53.8%) had CT changes compatible with NCC and six of the 28 (21.4%) tested positive in the enzyme-linked immunoelectro-transfer blot (EITB) assay. In a seizure-free random sample of this population, 17 of 118 (144 per 1000) subjects examined by CT and 10 out of 96 (104 per 1000) examined by EITB had evidence of this infection. The differences between the epilepsy group and the random sample of the population were statistically significant (OR = 6.93, 95% CI: 2.7-17.5, P < 0.001) for CT diagnosis, but not for EITB results (OR = 2.75, 95% CI: 0.8-7.1, P > 0.12, NS). CONCLUSIONS: These findings confirm that T. solium NCC is a significant cause of epilepsy at the community level in Andean villages of Ecuador. It is important to initiate effective public health interventions to eliminate this infection, which may be responsible for at least half of the cases of reported epilepsy in Ecuador.

Intractable headaches have been described as the presenting complaint of many patients with T. solium neurocysticercosis. We conducted a house-to-house neuroepidemiological survey of 2,723 residents of an Andean community, known to be endemic for this infection. Migraine headaches were confirmed in 187 cases (68.7 per thousand), and tension headaches were diagnosed in 77 cases (28.3 per thousand). Fifty-seven migraine sufferers accepted computed tomography examination, and in 19 it revealed neurocysticercosis. In 11 out of 52 migraineurs who had their blood drawn, electron immunotransfer blot testing (EITB) was positive for anticysticercal antibodies. In a computer-generated random sample of this community, 109 headache-free individuals were examined by CT, and 87 had EITB. Of the 109 subjects examined by CT, 14 were positive for cysticercosis. Of the 87 individuals tested by EITB, 7 were positive. A statistically significant difference between the symptom-free general population and the migraine patients was obtained for both CT (odds ratio 3.39, P < 0.005) and EITB (odds ratio 3.07, P < 0.05) diagnosis of neurocysticercosis. Neurocysticercosis appears to be a significant risk factor for the presentation of migraine-type headaches in areas endemic for T. solium infection.