Human cysticercosis occurs throughout the globe, particularly in regions where pig cysticercosis is common. Taenia solium is found worldwide, but is more common where pork is part of the diet and humans live in close contact with pigs. Both the forms of tapeworm infections - taeniasis and cysticercosis are prevalent in the rural areas of developing countries, especially which have poor sanitation, pigs roaming freely and eating human stools. Therefore, high prevalences are reported in Mexico, Latin America, West Africa, Russia, India, Pakistan, North-East China, and Southeast Asia.
About 50-100 million people are diagnosed with cysticercosis globally. This number is possibly underestimated as many infections do not present any symptoms and may go undiagnosed. World Health Organization (WHO) estimates that 2.56-8.30 million cases of neurocysticercosis occur globally. Neurocysticercosis is one of the most common cause of adult-onset seizures throughout the world. In the past decades, the diagnosis of neurocysticercosis has improved a lot, which can be attributed to the development of CT (Computed Tomography) and MRI (Magnetic Resonance Imaging) scan of the brain.
In Central and South America, Southeast Asia, India, China, and Sub-Saharan Africa, cysticercosis is characterised as an endemic disease. Studies indicate that in Latin America and India, almost half of the adult-onset seizures are caused due to neurocysticercosis. The seroprevalence rate in Latin America is about 4.9-24% and in some rural South American communities is between 10-25%. In rural Vietnam, the approximated true prevalence of both the tapeworm infections is 13%. Studies also indicate that taeniasis and cysticercosis occur in eastern European countries. In the United States, about 2,000 patients are hospitalized for neurocysticercosis every year. The cases are more prevalent in Latin American immigrants living in regions like Texas, Arizona, and California. Some cases occur because of travelling to the endemic areas.
Recent neuroimaging studies in India advocate that the disease burden in India exceeds several other developing countries. Cysticercosis is one of the neglected diseases in the country and systematic population-based studies for the disease are deficient. Hence, cysticercosis is most likely under-reported in India. Neurocysticercosis is considered as one of the most common single cause of epilepsy/seizures in India. About 50% of Indian patients with partial seizures are caused due to Cysticercosis. It appears to be more prevalent in northern states of India, such as Uttar Pradesh, Punjab, and Bihar. The prevalence of active epilepsy reported by a community survey of 50,617 people in South India was 3.83 per 1000 and neurocysticercosis was diagnosed in 28.4% of the cases by CT scanning. Pig or porcine cysticercosis is also prevalent in India. A study reported that the prevalence of pig cysticercosis in Lucknow district, Uttar Pradesh was as high as 26%, about 40% of them had cysts in the brain. Previous studies had also reported the detection of cysts in the pigs in Kolkata, Chandigarh and the surrounding regions.
The tapeworm infection-treatment gap, the difference in the number of people who need care and those who receive care, is above 90% in rural India. This gap could be attributed to lack of knowledge, deficiency of medical facilities, social preconception of modern medicine, and belief in alternative treatment methods. This needs to be addressed urgently by extensive use of treatment modalities, available preventive chemotherapeutic agents and vaccines as well as health education.
Cysticercosis occurs due to swallowing of the tapeworm eggs excreted in the feces of people infected with adult tapeworm. Tapeworm infection is caused due to the consumption of food or water contaminated with tapeworm eggs and putting contaminated fingers in the mouth.
The following are the risk factors of cysticercosis: