Morphologic and Genotypic Characterization of Psoroptes Mites from Water Buffaloes in Egypt

Species delimitation of Psoroptes spp. and identity of the parasite in water buffaloes remain poorly defined. In this study, Psoroptes infestation on three water buffalo farms in Egypt was examined based on morphometric characteristics, especially the opisthosomal setae of adult male mites. Clinical investigations showed that 28% (196/700) of the sampled animals had mange infestation. Microscopic examinations of 80 skin scrapings indicated the occurrence of Psoroptes mites in 17 (21.3%) samples, Sarcoptes mites in 27 (33.7%) samples, and the concurrence of both in 36 (45.0%) samples. Morphologically, the Psoroptes parasite was identified as Psoroptes natalensis. DNA sequence analysis of the second internal transcribed spacer (ITS2) in 11 representative samples confirmed the diagnosis and suggested the presence of a distinct variety of Psoroptes natalensis in Egypt.

Population identification and divergence threshold in Psoroptidae based on ribosomal ITS2 and mitochondrial COI genes

Psoroptidae mites are a type of small mites with a wide range of hosts. The proliferation of Psoroptidae mites could cause symptoms such as severe itching, atopic dermatitis, and hair loss in infected animals. If severely infected, death can also occur. The morphological classification and identification of Psoroptidae mites is problematic due to the overlapping geographical distribution. In addition, there is no divergence threshold for molecular classification and identification. To solve this problem, gDNA was extracted from individual Psoroptes and Otodectes mites (China) for amplification of rDNA ITS2 and mtDNA COI. After that, the sequences obtained were aligned and analyzed with those retrieved from GenBank. Based on rDNA ITS2 sequences, Psoroptidae was divided into three genera, namely, Psoroptes, Chorioptes, and Otodectes, which was in accordance with morphological classification. The intraspecies, interspecies, and intergenera could be differentiated effectively, with thresholds ≤ 5.20, 6.18-14.86, and ≥15.72 %, respectively. However, based on mtDNA COI sequences, Psoroptidae was divided into four genera with Caparinia added, as Caparinia sp did not cluster with the other three genera. The intra- and interspecies could be differentiated effectively, but interspecies and intergenera could not. The intra- and interspecies identification thresholds were ≤ 2.12 and ≥10.93 %. Further analysis showed that host but not geographical isolation was found in Psoroptes and Chorioptes, whereas Otodectes mites parasitizing dogs and cats were the same species; neither host nor geographical isolation was observed. In conclusion, rDNA ITS2 is better than mtDNA COI for DNA barcoding in Psoroptidae.

Transcriptomic analysis of circulating leukocytes reveals novel aspects of the host systemic inflammatory response to sheep scab mites

Infestation of ovine skin with the ectoparasitic mite Psoroptes ovis results in the development of a rapid cutaneous inflammatory response, leading to the crusted skin lesions characteristic of sheep scab. To facilitate the identification of novel diagnostic and therapeutic targets, a better understanding of the host-parasite relationship in sheep scab is essential. Although our knowledge of the host's local cutaneous inflammatory response to sheep scab has increased in recent years, we still know relatively little about the mechanisms of this response at the systemic level. This study used a combined network and pathway analysis of the in vivo transcriptomic response of circulating leukocytes to infestation with P. ovis, during a 6 week period. Network graph analysis identified six temporally-associated gene clusters, which separated into two distinct sub-networks within the graph, representing those genes either up or down-regulated during the time course. Functional and pathway analysis of these clusters identified novel insights into the host systemic response to P. ovis infestation, including roles for the complement system, clotting cascade and fibrinolysis. These analyses also highlighted potential mechanisms by which the systemic immune response to sheep scab can influence local tissue responses via enhanced leukocyte activation and extravasation. By analysing the transcriptomic responses of circulating leukocytes in sheep following infestation with P. ovis, this study has provided key insights into the inflammatory response to infestation and has also demonstrated the utility of these cells as a proxy of events occurring at local tissue sites, providing insight into the mechanisms by which a local allergen-induced inflammatory response may be controlled.

Taxonomic priority in Psoroptes mange mites: P. ovis or P. equi?

The taxonomic priority of Psoroptes mange mites (Acari: Psoroptidae) is reviewed and the original species descriptions re-examined. The question of whether the name Psoroptes equi or Psoroptes ovis has priority has importance with respect to the descriptions used in any legislation required for compulsory treatment of infested animals. It is concluded that in the work by Hering [(1838) Nova Acta Physico-Medica Acadamiae Caesareae Leopoldino-Carolinae Naturae Curiosorum. Tomi 18, Pars 2, Vratislaviae und Bonn], which is generally assumed to present the type description, the first Psoroptes mite described is P. ovis, and that P. ovis (Hering 1838) should therefore, carry taxonomic priority for the synonomised genus.

Morphological and molecular comparison of host-derived populations of parasitic Psoroptes mites

Infestation by parasitic Psoroptes mites (Acari: Psoroptidae) is an important cause of economic loss and welfare problems in livestock in many areas of the world. At least five species within this genus have been recognized, based on the host infested, the infestation site and differences in length of the opisthosomal setae of adult male mites. Here the integrity of these species is considered by subjecting populations of mites from a range of host species and geographical locations to simultaneous morphological and molecular genetic analyses. Morphological analysis showed that there were significant differences in shape and size between mite populations from different hosts, and that length of the outer opisthosomal setae in males and the homologous seta in females were the most important distinguishing character in adults. However, considerable variation in outer opisthosomal seta length was evident within and between populations of mites, and differences were not clearly related to host-species or geographical origin and did not support the accepted species differences. Molecular characterization using sequence data from the mitochondrial second internal transcribed spacer (ITS-2) region and microsatellite markers found little or no consistent host-related variation between the mite population samples. The results suggest that there is no case for considering the Psoroptes mites from the different hosts examined as separate species and that the morphological variation observed therefore may represent phenotypic adaptation to the local microenvironment on particular species of host.

Expressed sequence tag survey of gene expression in the scab mite Psoroptes ovis--allergens, proteases and free-radical scavengers

Psoroptes ovis, the causative agent of sheep scab, is an important ectoparasitic mite infecting sheep, goats and cattle. Infection is characterized by an extensive dermatitis, scab formation and intense itching. Initial focal lesions spread outwards, coalesce and may extend over the whole body. The host response to infestation has all the characteristics of an immediate-type hypersensitivity reaction but the mite antigens and allergens which initiate this response are almost completely undefined. Here, 507 randomly selected cDNAs derived from a mixed population of P. ovis were sequenced and the resultant nucleotide sequences subjected to Cluster analysis and Blast searches. This analysis yielded 280 clusters of which 49 had > 1 sequence with 24 showing significant Blast X homology to another protein in the databases. There were 231 sequences which appeared on one occasion and 109 of these showed significant Blast X homology to other sequences in the databases. This analysis identified homologues of 9 different types of allergens which have been characterized in other allergic conditions such as responses to house dust mites. It also identified a number of cysteine proteases which may contribute to lesion development as well as several free-radical scavenging enzymes which may protect the mite from host immune effector responses.

Validity of species status of the parasitic mite Otodectes cynotis

A combined molecular and phenotypic approach was used to determine whether ear mites of the genus Otodectes (Acari: Psoroptidae) belong to a single species. The second internal transcribed spacer (ITS 2) of the rDNA of 16 isolates from 11 cats, two dogs, one arctic fox and two ferrets originating from four different continents was characterized. In addition, mites from dog, cat and arctic fox were investigated morphologically. Sequence comparisons revealed five different, but closely related genotypes which did not segregate according to host species or geographical origin. Morphologically, mites of the three host species did not differ significantly in their body or leg sizes. These investigations support the view that ear mites of the genus Otodectes from different hosts and geographical origins belong to a single species, Otodectes cynotis (Hering).