Pediculosis capitis risk factors in schoolchildren: hair thickness and hair length.

The human head lice is a cosmopolitan ectoparasite that causes pediculosis. The main way of spreading lice is through direct head-to-head contact. It is popular knowledge that some individuals are more susceptible to contracting head lice than others. Reports of individuals who have never been affected by the disease are common, even living in the same environment and under the same conditions as people who regularly have lice infestations. Previous research has been carried out on the risk of this infection associated with different human factors like gender or age. However, studies on the influence of the individual hair characteristics are scarce. The objective of the study was to analyze the pediculosis risk using geographical location, gender, age and individual hair characteristics as variables. Pediculosis was diagnosed through the detection of living lice in the hair. This cross-sectional school-based epidemiological study was conducted in 310 schoolchildren aged 1 to 13 years of schools in 4 municipalities situated in the State of Paraná, Brazil. The prevalence of head louse infection in primary school students was 49.35 %. The Odds Ratio of presence of pediculosis (OR) was estimated using multivariate logistic regression analysis. The results obtained indicate that hair length and thickness increase the risk of infection. Furthermore, the inclusion of hair color, hair shape, kind of hair-scale as covariates increases the risk of pediculosis, indicating that these variables partly explain this susceptibility and that pediculosis is independent of gender. A smaller hair diameter may favor insect fixation to the hair in the nymphal phases. These results may explain why girls are a greater risk as they let their hair grow for cultural reasons, i.e., being of female gender is an agglutinating variable. The conclusions drawn may explain the discrepancies obtained in previous analyses.

Variability of Calodium hepaticum eggs from sigmodontine host species through geometric morphometric analysis.

Calodium hepaticum is a zoonotic nematode with a worldwide distribution. Although the host range of C. hepaticum includes a wide spectrum of mammals (including humans), this parasite is predominantly associated with the families Muridae and Cricetidae. Several Sigmodontinae species from Argentina were found to be infected by C. hepaticum, with a high prevalence in Akodon azarae. The present study focuses on C. hepaticum eggs from natural infection of three species of sigmodontine rodents from Argentina. Eggs were genetically characterized (intergenic 18S rRNA region). The objectives of this work are: (i) to propose a new analytical methodology; and (ii) to morphologically characterize C. hepaticum eggs, from three Sigmodontinae species (A. azarae, Calomys callidus and Oligoryzomys flavescens). Analyses were made by the Computer Image Analysis System based on the new standardized measurements and geometric morphometric tools. The resulting factor maps clearly illustrate global size differences in the parasite eggs from the three Sigmodontinae species analysed. The degree of similarity between egg populations was assessed through pairwise Mahalanobis distances, showing that the largest distances were detected between parasite eggs from C. callidus and O. flavescens. Herein, the phenotypical plasticity of C. hepaticum eggs is shown. Significant positive correlations were obtained between each egg parasite principal component 1 and rodent corporal characteristics: weight; liver weight; rodent length; and rodent body condition. The usefulness of the geometric morphometric analysis in studies of the relationship between C. hepaticum and its host must be highlighted. The high prevalence observed in A. azarae, associated with the wide size range of the parasite eggs evidenced by principal component analysis, suggests A. azarae to be the Sigmodontinae host species that plays the most important role as reservoir host for C. hepaticum in the New World.

Calodium hepaticum (Trichuroidea: Capillariidae) Infection In Akodon azarae: First Description of Histopathological Lesions In Sigmodontinae.

Calodium hepaticum (Trichinellida: Capillaridae) is a parasitic nematode of mammals distributed worldwide. Although this parasite can infect the liver of a wide diversity of mammals (including humans), it is mostly associated with Muroidea hosts. Sigmodontinae rodents were recently recognized as important hosts of this parasite in Argentina, but the impact of this parasitism on these hosts has not been established. Here we report results of histopathological analyses of 40 livers of Akodon azarae infected with C. hepaticum. Lesions were classified into 4 categories: level 0, absence of lesions; level 1, with focal granulomatous hepatitis; level 2, presence of multifocal granulomatous hepatitis, fibrosis and focal necrosis with neutrophils, and level 3, absence of intact adult parasites, diffuse distribution, necrosis, and fibrosis. Most samples presented lesions of level 2 (55%), but all categories of lesions were found. This is the first study to describe the lesions caused by C. hepaticum in the liver of Sigmodontinae rodents, and the results suggest that infection by this parasite is costly to A. azarae populations.