Taenia solium cysticercosis hotspots surrounding tapeworm carriers: clustering on human seroprevalence but not on seizures

Abstract

Background: Neurocysticercosis accounts for 30%-50% of all late-onset epilepsy in endemic countries. We assessed the clustering patterns of Taenia solium human cysticercosis seropositivity and seizures around tapeworm carriers in seven rural communities in Peru.

Methodology: The presence of T. solium-specific antibodies was defined as one or more positive bands in the enzyme-linked immunoelectrotransfer blot (EITB). Neurocysticercosis-related seizures cases were diagnosed clinically and had positive neuroimaging or EITB.

Principal findings: Eleven tapeworm carriers were identified by stool microscopy. The seroprevalence of human cysticercosis was 24% (196/803). Seroprevalence was 21% >50 m from a carrier and increased to 32% at 1-50 m (p = 0.047), and from that distance seroprevalence had another significant increase to 64% at the homes of carriers (p = 0.004). Seizure prevalence was 3.0% (25/837) but there were no differences between any pair of distance ranges (p = 0.629, Wald test 2 degrees of freedom).

Conclusion/significance: We observed a significant human cysticercosis seroprevalence gradient surrounding current tapeworm carriers, although cysticercosis-related seizures did not cluster around carriers. Due to differences in the timing of the two outcomes, seroprevalence may reflect recent T. solium exposure more accurately than seizure frequency.

Figure 1. Proportion seroprevalence of human cysticercosis and location of T. solium tapeworm carriers and NCC-related cases, Tumbes, Peru, 1999.

Two households with tapeworm carriers in Matapalo are virtually superimposed and cannot be differentiated visually. In the absence of defined community boundaries, straight lines were drawn to delimit villages respecting the self-reported area of residence data provided by each household.

Figure 2. Household-level prevalence of human cysticercosis seroprevalence and NCC-related seizure by distance to the nearest T. solium tapeworm carrier, Tumbes, Peru, 1999.

Observed prevalence rates in both figures are slightly jittered, and seizure frequencies 50% and 100% are represented as 40%.