Abstract
BackgroundTrichostrongylus is one of the most important zoonotic trichostrongylid nematodes, infecting mostly livestock. Data on its genetic characteristics are lacking in Iran.MethodsWe determined the phylogenetic relationships of Trichostrongylus species in three counties of Kohgiloyeh and Boyerahmad (K-B) province, southwest Iran. Small intestine and abomasum of 70 sheep and goats were investigated.ResultsA total of 35 isolates of Trichostrongylus worms were detected and all were genetically identified as Trichostrongylus vitrinus. Analysis of 321 bp of the internal transcribed spacer 2 (ITS2) of ribosomal DNA revealed 16 genotypes. All genotypes were single nucleotide polymorphisms, including some hypervariable points. All sequences were trimmed to 170 bp, compared with sequences on GenBank including short sequences from other endemic foci of Iran and other countries and all isolates were used to generate a maximum likelihood phylogenetic tree, which consisted of two clades A and B. Clade A included isolates from Iran, Russia, New Zealand, Australia and the UK; clade B only contained South African isolates. Most clade A isolates (north, southwest and west Iran, Russia, New Zealand, Australia and UK) were in a similar phylogenetic position. One subclade was detected in clade A (isolates from Southwest Iran, New Zealand and UK).ConclusionsWe hypothesize that drug resistant T. vitrinus may account for its exclusive detection in our samples. The high similarity of genotypes from Iran, New Zealand and UK may be due to their close political relationships during the colonial era. More research is needed to understand better the phylogeny of T. vitrinus and its relationship with drug resistance and human transmission.
Highlights
Trichostrongylus is one of the most important zoonotic trichostrongylid nematodes, infecting mostly livestock
Amplification of the internal transcribed spacer 2 (ITS2) fragment resulted in bands of about 321 bp for all 35 isolates and identified 16 different genotypes
In Khuzestan Province (West Iran), T. vitrinus, T. colubriformis [40] and in Golestan Province in North Iran, T. axei were isolated from goats and sheep [41]
Summary
Trichostrongylus is one of the most important zoonotic trichostrongylid nematodes, infecting mostly livestock. Parasitic infections affect populations all over the world, especially in developing countries. Trichostrongylosis in livestock has been reported from diverse geographical settings, including Southeast Asia. Ghatee et al Parasites Vectors (2020) 13:553. Iran is one of the main foci of livestock and human infections and trichostrongylosis has been reported frequently [17, 18]. The life-cycle of Trichostrongylus spp. is direct, simple and without an intermediate host. Host infection occurs upon ingestion of filariform larvae found in contaminated vegetables or water. These larvae migrate to the small intestine or abomasum, grow to adults which mate and produce eggs that are excreted in the feces into the external environment. Under optimal temperature and humidity, rhabditiform larvae hatch from eggs within a few days and, after two moltings (L1 and L2) over 5 to 10 days, become infective filariform larvae (third-stage) [3, 19]
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