Seroprevalence of Toxocara canis infection in tropical Venezuela

Abstract

An enzyme-linked immunosorbent assay (ELISA) was used to determine the seroprevalence of Toxocara canis infection in different socio-economic groups of the tropical population of Venezuela. The lack of definitive independent diagnostic criteria for toxocariasis required the establishment of operational upper limits of normality for Toxocara ELISA values, based upon their log-normalized distribution in a presumptive "non-toxocariasis" sub-population. Only 1.8% of urban subjects of medium-high socio-economic level were considered to be clearly positive in Toxocara ELISA, compared to 20.0% of urban slum dwellers, 25.6% rural subsistence farmers and 34.9% Amazon Indians. As the test was performed using excretory-secretory antigen, and under conditions of competitive inhibition by soluble extracts of non-homologous parasites, co-infection by common intestinal helminths, protozoa or other organisms did not give rise to false positive results. However, strong cross-reactivity with Onchocerca volvulus may have influenced the prevalence figure obtained for the Amazon Indians. These results indicate that T. canis is yet another parasite that is widely distributed in economically underprivileged tropical populations.

Human toxocariasis: a seroepidemiological survey in the Amazonian city of Yurimaguas, Peru

“…This value is among the values of frequency previously found in other places from our country [7][8][9]30,31 and relatively similar with other studies from other Latin American countries 2,3,21,27 .…”

“…*Some subjects had more than one sign/symptom; **p < 0.05 = significant value (Chi-square); *** variables in the model: sex, age, pulmonary and hepatic manifestations, headache, and weakness and/or fatigue. In agreement with other authors, we have also found statistically significant differences between gender and positive serology indicating that male subjects are more associated at risk of toxocariasis than female subjects, probably because of their close contact with soil, as is the case with this population, who are farmers 4,5,21,22,26 .…”

“…The frequency of human infections by larval stages of Toxocara is high in tropical and developing countries, and is generally associated with low socioeconomic groups 15 , with rates ranging from 1% in Spain 25 to 86% in Santa Lucia 36 ; from 3.6% to 24.7% in Brazil 2,4 ; 47.5% in Colombia 1 ; from 34.9% to 66.6% in Venezuela 10,21 , and from 37.9% to 39% in Argentina 3,27 . In Peru, a few reports have informed of frequencies from 7.8% to 44.92% in rural populations from different places [7][8][9]19,30,31 .…”

Frequency of human toxocariasis in a rural population from Cajamarca, Peru determined by DOT-ELISA test

“…Different rates have been reported ranging from 1% in Spain 28 to 86% in Santa Lucia 35 ; 3.6% to 24.7% in Brazil 2,9 ; 47.5% in Colombia 1 ; 34.9% to 66.6% in Venezuela 14,22 , and 37.9% to 39% in Argentina 3,30 . In Peru, limited reports indicate frequencies of 7.8% to 20% in rural population and 40% in subjects with ocular suspicion 12,13,21 .…”

Toxocariasis in the Americas: Burden and Disease Control

“…The first studies in the country found up to 66.6 % seroprevalence in children 2 -7 years old of Caracas [59]. In Ameridians from the Venezuelan Amazon region, a seroprevalence of 34.9 % was reported in 1988 [60]. Most studies in the country have been limited to short case series or even case reports.…”