Differentiation of Trichuris species using a morphometric approach

Abstract

Trichuris trichiura is a nematode considered as the whipworm present in humans and primates. The systematics of the genus Trichuris is complex. Morphological studies of Trichuris isolated from primates and humans conclude that the species infecting these hosts is the same. Furthermore, numerous molecular studies have been carried out so far to discriminate parasite species from humans and Non-Human Primates using molecular techniques, but these studies were not performed in combination with a parallel morphological study. The hypothesised existence of more species of Trichuris in primates opens the possibility to revise the zoonotic potential and host specificity of T. trichiura and other putative new species of whipworms. In the present work, a study of Trichuris Roederer, 1761 (Nematoda:Trichuridae) parasitizing C. g. kikuyensis , P. ursinus , Macaca sylvanus , Pan troglodytes , and Sus scrofa domestica has been carried out using modern morphometric techniques in order to differentiate populations of Trichuris isolated from four species of captive NHP from different geographical regions, and swine, respectively. The results obtained revealed strong support for geometrical morphometrics as a useful tool to differentiate male Trichuris populations. Therefore, morphometrics in combination with other techniques, such as molecular biology analyses, ought to be applied to further the differentiation of male populations. On the other hand, morphometrics applied to female Trichuris species does not seem to contribute new information as all the measurements combinations of obtained from females always showed similar results.

Trichuris trichiura isolated from Macaca sylvanus: morphological, biometrical, and molecular study

“…Thus, this can be differentiated from T. colobae by the presence of a typical subterminal paracloacal papillae but not associated to a cluster of small papillae and a different spicule to that of T, colobae and T. ursinus , while females presented a non-everted vagina with a non-ornamented vulva. From a biometrical point of view, a preliminary study [ 29 ], based on modern morphometric approach, revealed that the analysis based on three measurements of males (maximum width of the posterior region of the body [thickness, M4], length of the spicule [M8], maximum length of the spicule sheath [M9], clearly illustrates globalized differences in the population of Trichuris sp. from M. sylvanus showing larger values of the males collected from the macaques with respect to T. trichiura from chimpanzees [ 7 , 29 ].…”

“…From a biometrical point of view, a preliminary study [ 29 ], based on modern morphometric approach, revealed that the analysis based on three measurements of males (maximum width of the posterior region of the body [thickness, M4], length of the spicule [M8], maximum length of the spicule sheath [M9], clearly illustrates globalized differences in the population of Trichuris sp. from M. sylvanus showing larger values of the males collected from the macaques with respect to T. trichiura from chimpanzees [ 7 , 29 ]. The occurrence of different biometrical measurements in the same species was explained by Nissen et al [ 9 ] as phenotypic adaptations [ 1 ].…”

“…Biometrical analysis of Trichuris specimens was carried out according to parameters reported by Spakulová and Lýsek [ 15 ], Suriano and Navone [ 16 ] and Robles et al [ 17 ]. Subsequently, a biometrical study was carried out using those measurements that are significant in the differentiation of Trichuris species and reported previously by García-Sánchez et al [ 29 ]. Descriptive univariate statistics (mean values, standard deviations, and range) for all parameters were determined for all individuals of Trichuris sp.…”

“…The Student’s t assess was used to test the equality of means for each variable in both lineages. The following non-redundant measurements (one measurement is not included in another) used for whipworm adults were: Total length, esophagus length (EL), body length (BL), ratio EL/BL, wide body, spicule length, spicule length sheath for male; total length, esophagus length, body length, ratio EL/BL, wide body and vulvar diameter for females [ 29 ]. It was considered a value statistically significant when P < 0.05.…”

“…The principal component analysis (PCA) was used to summarize most of the variations in a multivariate dataset in a few dimensions. The multivariate analyses of the morphometric data were carried out by using BAC v.2 software [ 29 , 40 , 41 ].…”