Research Article: Estimating the Non-Monetary Burden of Neurocysticercosis in Mexico

Date Published: February 21, 2012

Publisher: Public Library of Science

Author(s): Rachana Bhattarai, Christine M. Budke, Hélène Carabin, Jefferson V. Proaño, Jose Flores-Rivera, Teresa Corona, Renata Ivanek, Karen F. Snowden, Ana Flisser, Jakob Zinsstag.

Abstract: BackgroundNeurocysticercosis (NCC) is a major public health problem in many developing countries where health education, sanitation, and meat inspection infrastructure are insufficient. The condition occurs when humans ingest eggs of the pork tapeworm Taenia solium, which then develop into larvae in the central nervous system. Although NCC is endemic in many areas of the world and is associated with considerable socio-economic losses, the burden of NCC remains largely unknown. This study provides the first estimate of disability adjusted life years (DALYs) associated with NCC in Mexico.MethodsDALYs lost for symptomatic cases of NCC in Mexico were estimated by incorporating morbidity and mortality due to NCC-associated epilepsy, and morbidity due to NCC-associated severe chronic headaches. Latin hypercube sampling methods were employed to sample the distributions of uncertain parameters and to estimate 95% credible regions (95% CRs).FindingsIn Mexico, 144,433 and 98,520 individuals are estimated to suffer from NCC-associated epilepsy and NCC-associated severe chronic headaches, respectively. A total of 25,341 (95% CR: 12,569–46,640) DALYs were estimated to be lost due to these clinical manifestations, with 0.25 (95% CR: 0.12–0.46) DALY lost per 1,000 person-years of which 90% was due to NCC-associated epilepsy.ConclusionThis is the first estimate of DALYs associated with NCC in Mexico. However, this value is likely to be underestimated since only the clinical manifestations of epilepsy and severe chronic headaches were included. In addition, due to limited country specific data, some parameters used in the analysis were based on systematic reviews of the literature or primary research from other geographic locations. Even with these limitations, our estimates suggest that healthy years of life are being lost due to NCC in Mexico.

Partial Text: Neurocysticercosis (NCC) is a major public health problem caused by the larvae of the zoonotic cestode Taenia solium. Humans are the definitive hosts of T. solium and become infected with the intestinal adult tapeworm (taeniasis) by ingesting undercooked pork containing cysticerci. Humans can also become accidental intermediate hosts after ingesting T. solium eggs leading to cysticercosis and/or NCC, which occurs when larvae develop in the central nervous system. A recent meta-analysis of published studies on the frequency of NCC estimated that 29% (95% CI: 23%–36%) of epilepsy cases in NCC-endemic areas exhibit NCC lesions as identified by brain neuroimaging [1]. NCC may also manifest as migraine-type headaches and stroke, among others [2], [3].

This study represents only the second study to estimate the burden of NCC using DALYs. The first, which was conducted in Cameroon, estimated human NCC burden based on epilepsy alone [10]. The estimated number of DALYs lost per 1,000 person-years was higher in Cameroon (9.0) compared to Mexico (0.25). One difference between the two studies is that all of our data were stratified by urban/rural areas, age groups, and gender. Such stratification was not used in the Cameroon study. Since the majority of the Mexican population is urban, and the proportion of epilepsy cases attributable to NCC is lower in urban areas, the overall burden per person is expected to be lower in Mexico. In addition, NCC-associated epilepsy patients were four times more likely to receive treatment in Mexico than in Cameroon. Because the disability weight for treated epilepsy is much lower than that for untreated epilepsy, this results in fewer DALYS per 1,000 person-years.