Horse bots are the parasitic larvae of the botflies, Gasterophilus spp. Adult females deposit their eggs onto hair shafts of horses. Bot larvae are eventually ingested through grooming and can cause inflammatory reactions during migration within the oral cavity and by attachment to the stomach wall. In general, bot larvae are considered benign, even though some pathology is observed. Bot larvae can be identified during oral inspection or gastroscopy.
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We'd like to understand how you use our websites in order to improve them. Register your interest. Gasterophilus species are widely distributed around the world. The larvae of these flies parasitize the digestive tract of equids and cause damage, hindering horse breeding and protection of endangered species.
However, study of the genetic structure of geographically distinct Gasterophilus populations is lacking. Here, we analyzed the genetic diversity of Gasterophilus pecorum , G. Haplotype diversity and nucleotide diversity of mitochondrial genes was generally high in all Gasterophilus populations.
Due to the unique natural climatic conditions of the alpine steppe, there were high levels of genetic differentiation among different geographical populations of G. Frequent exchanges between meadow and desert steppe Gasterophilus species resulted in low genetic differentiation.
The highest exchange rates were found among G. Genetic differentiation was only observed on a large geographical scale, which was confirmed by analyzing population genetic structure. Three species, G. Our results show that the four Gasterophilus species have a high level of genetic diversity and different degrees of genetic differentiation and gene flow among different populations of the same species, reflecting their potential to adapt to the environment and the environmental impact on genetic structure.
Knowledge of the genetic structure, population history, and migration will help understand the occurrence and prevalence of gasterophilosis and provide a basis for controlling the local spread of Gasterophilus spp.
Gasterophilus species are common obligate parasites in equines and are widely distributed worldwide. The genus Gasterophilus Diptera: Oestridae includes nine species [ 1 ]; of these, six are found in China: G.
Gasterophilus larvae parasitize the gastrointestinal tract of equids for 10—11 months and cause mucosal lesions, gastrointestinal ulcers, peritonitis, anemia and gastric rupture, which can be severely debilitating [ 5 , 6 ]. In European and American countries where animal husbandry is highly developed, the most prevalent species are G. In traditional Chinese pastoral areas i. Inner Mongolia, Xinjiang and Qinghai the distribution of Gasterophilus larvae is more complicated than in other regions.
Six species of Gasterophilus were found in Inner Mongolia, the predominant species being G. The diversity index of Gasterophilus in this region was found to be 1. Mitochondrial DNA markers have been widely used in studies of insect taxonomy, population genetics and evolution.
More specifically, mitochondrial cytochrome c oxidase cox 1 and cox 2 genes have been used to examine inter- and intraspecific relationships in Diptera, Lepidoptera, Coleoptera, Hymenoptera and Hemiptera [ 15 , 16 , 17 , 18 , 19 ]. Previous investigations based on partial mitochondrial cox 1 gene sequences revealed a high degree of genetic diversity that enabled differentiation of the Italian and Polish populations by PCR-restriction fragment length polymorphism [ 20 ].
However, little is known about the genetic structure of geographically distinct Gasterophilus populations. In the present study, we explored the population genetic structure and haplotype distribution patterns in several populations of G.
A total of 97 G. Larvae were preserved in ethanol and identified based on morphology [ 1 ]. Among the sampling sites in this study, KNR of Xinjiang Uigur Autonomous Region is located in the desert subregion of northwestern China with an altitude of — m, average annual temperature of 2. DL is located at the southern end of Xilin Gol Grassland in Inner Mongolia and is part of the Eurasian steppe; it has an elevation of — m, average annual temperature of 1. Xinjiang and Inner Mongolia are zoogeographical regions belonging to the same district in China [ 24 , 25 ].
MD is located in southwest Qinghai Province northwest of Guoluo Tibetan Autonomous Prefecture and has a plateau continental climate, the altitude is — m, annual average temperature is PCR amplification of cox 1 was performed according to a previously described protocol [ 20 ].
Sequences generated in this study as well as published sequences of G. Raw sequences were proofread and edited using BioEdit v. DnaSP v. Phylogenetic trees were constructed by the neighbor-joining NJ method using MEGA and were assessed with bootstrap replicates [ 32 ]. Haplotype networks were constructed using TCS v.
The search strategy included three replications of 10 short initial chains and two long final chains. The initial chains were run with samples and the sampling interval was set to The final chains were performed with 10, samples with the same sampling interval.
A burn-in of samples was used for each chain. A total of cox 1 sequences were obtained for G. An analysis of all cox 1 sequences identified a total of haplotypes.
For each species, only two to five common haplotypes were observed within localities in China and there were no shared haplotypes across G. The cox 2 sequences of the four Gasterophilus species defined haplotypes. Similar to cox 1, only two to six common cox 2 haplotypes were observed within populations of each species. The minimum spanning network calculated with TCS software using cox 1 haplotypes of G. The sub-networks formed a star-like structure that was derived from haplotype GpH4.
Haplotypes in the KNR population were more evenly distributed throughout the network. In general, the cox 2 haplotypes formed two sub-networks with GpH17 and GpH43 as the central haplotypes Fig. The haplotype distribution of each geographical population was similar to that of cox 1. Individuals in the GpHcentric sub-network were the same as those in the cox 1 haplotype sub-network comprising only MD haplotypes. Haplotype networks for G. The network structure was dominated by a single haplotype GiH4 Fig.
Haplotypes from Italy and Poland were all private haplotypes i. The cox 2 haplotype network had a star-like structure, with the most abundant haplotype GiH6 in the center and distributed across all geographical regions KNR and DL Fig. All haplotypes from Italy and Poland were private.
Haplotypes in Poland constituted a separate sub-network, while those in Italy were less directly linked to haplotypes from localities in China. The cox 2 haplotype network was dominated by GnH16, which was represented by a single individual Fig. The MD haplotypes were mostly focused on branches centered on GnH5, there was no similar phenomenon in the cox 1 haplotype network.
Most GL haplotypes were distributed around GniH The cox 2 haplotype network comprised a single network centered around haplotype GniH16 Fig. Five of the 22 haplotypes differed by more than eight mutations from haplotype GniH16, and most DL haplotypes were more closely related to the ancestral one. The phylogenetic tree constructed with the NJ method based on the cox 1 gene included 48 haplotypes divided into seven clades Fig.
Clade 1 included Clades 3 and 7 comprised An NJ tree constructed from cox 2 sequences had five clades Fig. DL haplotypes, including nine that were private, were mainly distributed in Clades 2 and 3, accounting for Clades 1 and 5 contained the remaining 13 private haplotypes of MD except for GpH35, and included Neighbor-joining tree based on the cox 1 gene for G.
The NJ tree constructed based on the cox 1 gene included 44 haplotypes that were divided into four clades Fig. Haplotypes from Italy and Poland were independently clustered and all were distributed in Clade 2, with the populations from the four geographical regions of China forming the three remaining clades. The NJ tree constructed based on cox 1 haplotypes had three clades Fig. The NJ tree constructed based on the cox 2 gene had 31 haplotypes divided into three clades Fig.
The KNR population was mainly distributed in Clade 1, which included 10 private haplotypes and All four private haplotypes of MD were distributed in clade 3, which included The DL population was distributed in three clades with no obvious aggregation.
The NJ tree constructed from cox 1 haplotypes was divided into three clades Fig. The DL population was mainly distributed in Clade 1, which contained eight private haplotypes and The NJ tree constructed based on cox 1 haplotypes was also divided into three clades Fig.
The private haplotypes of DL were all distributed in Clade 1, which included The haplogroup clustering of the KNR population was similar to that of cox 1. Mean genetic distances between different populations were calculated based on cox 1 and cox 2 sequences.
These results demonstrate that the genetic distance was smallest between KNR and DL populations and larger than for other populations. Fst values for cox 1 sequences were 0. Fst values for cox 2 sequences were 0. Genetic distances among different populations based on cox 1 sequences are shown in Table 1.
Mean genetic distances among Chinese, Italian and Polish populations ranged between 0. The distances among populations in China did not differ significantly 0. Fst and Nm values for cox 1 sequences among the six populations are shown in Table 2. Mean genetic distances among populations based on cox 1 sequences are shown in Table 3. Distances based on cox 2 sequences were 0. The sequence dataset for cox 2 also revealed a close genetic distance between KNR and DL and showed that MD was distant from the other populations.
Fst and Nm values for the cox 1 gene among the four populations are shown in Table 4. The mean genetic distances between KNR and DL populations calculated based on cox 1 and cox 2 sequences were 0. Populations are often far from equilibrium, and not all deviate in the same direction. Among G.
Gasterophilus Spp. Infections in Horses From Northern and Central Kazakhstan
The species Gasterophilus is of the family Oestridae , and is more commonly referred to as the 'Bot fly. Within the United Kingdom there are three species of veterinary importance; G. Gasterophilus are medium to large flies at mm long, and are thought to look similar to drone bumble bees. Both G. Eggs are laid on the body of the host and either hatch spontaneously or are stimulated to hatch through an increase in warmth and moisture from the animal self-grooming. They are laid in different areas according to species; G.
Horse gastrointestinal myiasis caused by larvae of Gasterophilus spp. Diptera, Oestridae flies has a worldwide distribution and, where present, it is primarily caused by larvae of Gasterophilus intestinalis and Gasterophilus nasalis. Other species, i. With the aim to contribute data on the species composition of Gasterophilus and on the seasonal variation of the infection pattern in southern Italy, native horses were necropsied from January to December and Gasterophilus larvae were collected from the stomach, the small intestine and the rectum of each of them. On the whole, Five species of Gasterophilus were identified with the following prevalence: G.
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