Combined Molecular and Lectin Binding Assays to Identify Different Trichostrongyle Eggs in Feces of Sheep and Goats from Egypt

Abstract

Trichostrongyles are common causes of parasitic gastroenteritis in sheep and goats worldwide. Accurate identification of these nematodes to the genus and/or species level is important for therapy selection and control strategies. In the present study, molecular and egg-lectin binding approaches were employed to identify the most economically important trichostrongyles circulating in sheep and goat herds from six districts in Dakahlia governorate, Egypt. Fecal samples from 653 and 205 goats reared within 17 herds were collected and tested for the trichostrongyle eggs using the modified Wisconsin sucrose flotation method. For identification of the trichostrongyle(s) present, eggs from 75 (63 sheep and 12 goats) samples which had high egg count (EPG) and pooled eggs (n = 19 pools, 15 sheep and 4 goats) from samples with moderate or low EPGs were examined. Molecular examination was conducted amplifying the ITS2 region of the rDNA for six different trichostrongyles in individual PCR reactions. For egg-lectin bindings, 4 fluorescently-labeled specific lectins were used; peanut agglutinin (PNA) for Haemonchus contortus, Aleuria aurantia agglutinin (AAL) for Trichostrongylus species, Lens culinaris agglutinin (LCA) for Teladorsagia circumcnicta and Lotus tetragonolobus lectin (LTL) for Cooperia species. Fourteen (82.3%) herds were found infected, of which trichostrongyle eggs were detected in fecal samples of 26.5% (173/653) of sheep and 10.2% (21/205) of goats. Results of the PCR and lectin bindings were compatible and 4 trichostrongyles were detected: H. contortus, T. circumcincta, Trichostrongylus axei and Trichostrongylus colubriformis. Haemonchus contortus eggs were found in all the infected herds, and as the single species in 21 and 5 of sheep and goat samples, respectively. Lectin stained smears demonstrated the dominance of H. contortus eggs over eggs of the other detected trichostrongyles. Eleven herds were found infected with T. axei as the second most prevalent trichostrongyle; however, few AAL-stained eggs were noticed in the positive samples. Mixed infections were frequently detected as H. contortus-T. axei combination. Infections with T. circumcincta were noted in sheep samples from two herds, but not in any sample from the goats. No Ostertagia leptospicularis, Cooperia curticei or Nematodirus species were noted among the tested samples. This is the first molecular and lectin binding survey to determine the species composition of trichostrongyles infecting sheep and goats from Egypt. Haemonchus contortus plays the principal role in small ruminant trichostrongylosis in Egypt. Egg-lectin staining shows promise for future for its application in routine diagnosis as a rapid and simple technique. Findings of the earlier reports from Egypt are tabulated and reviewed.