Observations on the epizootiology of gasterophilus intestinalis and G. nasalis in horses in morocco

Oviposition site selection by Gasterophilus pecorum (Diptera: Gasterophilidae) in its habitat in Kalamaili Nature Reserve, Xinjiang, China

Oviposition site selection is an important aspect of the behavioural ecology of insects. A comparison of the habitats used by a species enhances our understanding of their adaptation to altered environments. We collected data on the oviposition behaviours of Gasterophilus pecorum (Diptera: Gasterophilidae) in its habitat in Kalamaili Nature Reserve (KNR), Xinjiang, China between March and October 2014. We found 91 quadrats were used by G. pecorum for oviposition. Examining 13 ecological factors using the t-test, chi-square test, and principal component analysis showed that G. pecorum's oviposition habitat was preferentially on slopes with inclinations of 10-30° that were semi-sunny, semi-cloudy slopes, in positions high or low on the slopes, with preferences for total plants lower than 10% and Stipa capillata coverage lower than 10% on the low slopes, but Ceratoides latens coverage on the high and intermediate slopes, when the numbers of plant species and families were lower than five. G. pecorum often selected sites at a distance < 2000 m from a water source and average altitude 900-1000 m. The oviposition site selection by G. pecorum may be correlated with the behaviour of Przewalski's horses (Equus ferus przewalskii), and water and food resources may strongly influence oviposition site selection, as Przewalski's horses rest and forage in these areas.

Gasterophilus spp. infections in horses from northern and central Kazakhstan

A cross-sectional survey was performed to obtain current data on the gastrointestinal myiasis of horses in the provinces of Kostanay, Akmola and Karagandy, northern and central Kazakhstan. The stomach, small intestine and rectum of 148 slaughter horses were examined for Gasterophilus spp. larvae during a 26-month study period. All horses were infected with 2nd and 3rd stage larvae (mean intensity: 803±350), and 22% of them harboured >1000 Gasterophilus spp. larvae each. Four species were identified: G. intestinalis (prevalence: 100%; mean intensity: 361±240 larvae), G. haemorrhoidalis (100%; 353±191), G. nasalis (100%; 73±36) and G. pecorum (91.2%; 18±10). Horses aged<2 years were higher infected with Gasterophilus larvae than 2-4 years old animals. Both the prevalence and extremely high intensity of Gasterophilus infections of horses in these Kazakh regions suggest respective control measurements to improve the health and performance of the animals and to increase the economic income of horse owners.

Epidemiological observations on stomach worms of horses in Morocco

Six to nine horses per month (total of 94 in a year) were examined for stomach worms in the Settat region of Morocco. All the animals were infected by at least one helminth species. Habronema muscae occurred in 95–8%, H. majits in 75.6% and Trichostrongylus axeiin 80.9% of horses. Polyparasitism was observed in 93.6% of horses. Both for Habronema spp. and T. axei the peak worm burden was observed in November and minimum in June. The infection pattern Habronema spp. was directly related to the period of activity of fly vectors.

Prevalence and macro- and microscopic lesions produced by Gasterophilus nasalis (Diptera: Oestridae) in the Botucatu Region, SP, Brazil

The objective of the present study was to investigate the prevalence of Gasterophilus nasalis larvae in Botucatu, the central west region of São Paulo State, Brazil, and to describe the lesions caused by the parasite. The climate of Botucatu is warm and rainy during the months of December through March and cool and dry during the months of May through August. The prevalence of G. nasalis was 16.84%, and the period of peak infestation corresponded to the months of cold and dry weather. The lesions detected at the sites of larval attachment were examined macro- and microscopically. Erosions and ulcerations of the gastric mucosa and proximal duodenum were the major macroscopic lesions detected. Microscopically, the lesion spectrum ranged from mild inflammatory reactions to extensive necrosis and ulceration.

Field observations of the host-parasite relationship associated with the common horse bot fly, Gasterophilus intestinalis

Behavior of Gasterophilus intestinalis (Diptera: Gasterophilidae) was observed in the laboratory and field over a period of 10 years. Mating occurred in a frenzied manner as flies emerged from pupae. Males attempted to copulate with females that had not fully emerged from the pupal case. Mating was never observed in the field or near the horse. Observations suggest that fecal piles of the horse are used as the mating site for the newly hatched flies. Activation of host-seeking behavior was found to occur early and remain throughout the life span of the adult as it sought multiple hosts for oviposition. Evidence is presented supporting the use of olfaction and vision in finding the host. Interest by flies in shadows and linear high-contrast objects was observed. Methods used by the flies to maintain close proximity with the host are discussed including flight with the host and avoidance of host defenses. Recapture methods were successful in determining the time taken to reestablish at the host, and extent of travel to the host. The presence of kairomone(s) within horse secretions is suspected.

Gasterophilus intestinalis infections in horses in Belgium

Over a period of one year, from December 1995 to November 1996, larvae of Gasterophilus intestinalis were found in 193 horse stomachs (58%) of 330 that were examined in two Belgian slaughter houses. When August is excluded, 62% of the stomachs had bot larvae. No other Gasterophilus species were identified. The monthly prevalence ranged from 9% in August to 75% in November and December. The mean intensity of bot larvae varied from 8 in August to 29 in March, and the majority of the horses (67%) harboured less than 50 larvae. Prevalences and intensities were not affected by age, but mares were more frequently infected than stallions and geldings (P < 0.014). The mean size of the lesions increased from 1 cm2 to 17 cm2. The majority of the larvae were localised near the margo plicatus.

Epidemiological observations on Gasterophilus intestinalis and G. nasalis in donkeys from Morocco

During a 24 month period, 198 donkeys were examined for Gasterophilus intestinalis and Gasterophilus nasalis larvae. Gasterophilus intestinalis was found in 97.5% and G. nasalis in 95.5% of donkeys. The third instars (L3) of both species occurred during all months of the year and so did the second instars (L2), except in April (G. nasalis) and May (G. intestinalis). Over 75% of the animals had up to 200 larvae and 1.5% had over 600 larvae. The maximum number of both L2 and L3 larvae found in any animal was 418 G. intestinalis, 433 G. nasalis and 715 of both species combined. The seasonal variation in the numbers and development status of larvae indicated that the period of greatest activity of adult flies of G. intestinalis was from August/September to November, and that of G. nasalis from May to September. Consequently, the L2 larvae in the stomachs were in peak numbers between November and January for G. intestinalis and between July and September for G. nasalis. The L3 larvae of G. intestinalis had peak numbers between December and July, and those of G. nasalis between October and March. During January-March, most of the L2 larvae of G. nasalis were trapped in polypous nodules near the pyloric end of the stomach. It is concluded that the high-risk period for infection is during late spring and autumn, leading to the heavy larval burden of Gasterophilus in the stomach of donkeys during winter.

Effects of migrating Gasterophilus intestinalis larvae (Diptera: Gasterophilidae) on the mouth of the horse

Lesions were formed in the mouth of the horse by first- and second-stage Gasterophilus intestinalis larvae. The lesions resulted as larvae burrowed through the top millimeter of the tongue and then became embedded in the interdental gingiva. Appearance of the lesion was dependent on the degree of larval burrowing activity and healing that had taken place. Active tunneling production occurred at the posterior end of the lesion. Extensive change in configuration and color was apparent along the longer lesions with active larvae. Virtually all tissue in the path of the larvae was removed while forming a tunnel. Tissue destroyed included tops of the lamina propria mucosae evaginations and the deeper portions of the lamina epithelialis mucosae. Histopathologic findings showed that the tissue removed included the nerve and blood supply of the proprial evaginations. Hemorrhage and exocytosis into the tunnels included erythrocytes mixed with some macrophages, lymphocytes and scant numbers of eosinophils. Air shafts excavated in the tongue by larvae enabled bacteria to enter into the tunnels. Bacteria became adhered to larvae and initiated microabscesses. Microabscesses were composed of clotted erythrocytes, bacteria, disintegrating epithelial cells, and large numbers of neutrophils. Cells surrounding the tunnel exhibited pyknosis, epithelial hydropic degeneration and became separated from each other. Healing of tongue lesions occurred as epithelial cell growth below raised the tunnel upward and affected tissue desquamated. Interdental gingiva invaded by larvae were hyperemic and denuded of epithelia. Recession and ulceration of the gingiva produced periodontal pockets. Extensive invasion by larvae led to compound periodontal pockets. Larval mouth hooks were embedded in the submucosa of the pockets and tore at engorged capillaries. The cephalic portion of embedded larvae became surrounded by a cellular exudate containing erythrocytes and mononuclear cells. Attachment of second-stage larvae at the root of the tongue did not produce observable damage.

Observations on the occurrence of five species of Gasterophilus larvae in free-ranging horses in Umbria, central Italy

Comparative data collected over 4 years show the most frequent species of Gasterophilus infesting free-ranging horses in Umbria (Central Italy) to be G. intestinalis (93.8%), G. nasalis (76.5%) and G. inermis (71%). G. pecorum and G. haemorrhoidalis were less frequent and appeared in 39.3 and 10.8% of the animals, respectively. For each of the 5 species, the duration of gastric and enteric lesions, the average numbers of larvae isolated throughout the year and the probable duration of oral lesions were discussed.

Parasites of the stomach in donkeys of the highveld of Zimbabwe

Fourteen donkeys from a communal area of the Zimbabwean highveld were examined for stomach parasites during July and November of 1986 and January and April of 1987. All 14 animals were infected. Habronema muscae occurred in 12, Draschia megastoma in 11, H. majus in 9, Trichostrongylus axei in 9, Gasterophilus intestinalis in 14 and G. nasalis in 1 donkey. The lowest level of infection was in January for the helminths and in April for Gasterophilus larvae. The peak burdens of parasites were in July for Habronema spp. and in November for D. megastoma and Gasterophilus larvae. Infections with spirurid worms and Gasterophilus develop mainly from the middle of the rainy season to the beginning of the dry season (January to May/June). G. intestinalis seems to have an annual cycle.

Incidence and monthly prevalence of Gasterophilus spp. larvae (Diptera: Gasterophilidae) in the stomach of donkeys (Equus asinus) in Egypt

The stomachs of 118 donkeys were examined at postmortem during the period from March 1982 to February 1983 for Gasterophilus spp. larvae. G. intestinalis larvae clustered in groups near the boundary of the glandular and non-glandular epithelium of the stomach and infested 98.3% of the donkeys with highest numbers in July and lowest numbers in October. G. nasalis larvae were mainly attached near the pylorus and first part of the duodenum and infested 87.3% of donkeys with highest incidence in December and lowest in October. The ratio of the second and third instars of G. intestinalis to G. nasalis ranged from 71% to 29%. The percentage of donkeys infested with 1-100, 101-200 and 201-300 larvae was 72.0, 18.6 and 4.3% for G. intestinalis and 76.3, 8.5 and 0.8% for G. nasalis.

The prevalence of Gasterophilus intestinalis in horses in northern England and Wales

The stomachs of 448 horses from northern England and Wales were examined for Gasterophilus larvae, and 237 (52.7%) were found to be infected with G. intestinalis. Larvae were present in stomachs examined during each month of the year except August. Second instar larvae occurred from September through February and third instars were present from November through July. Adult fly activity began in August as indicated by the presence of eggs on horses. The life-cycle of G. intestinalis in northern England and Wales is outlined from the data presented. The mean instar burdens were 15.7 second and 38.0 third instars, and more than 75% of the infections consisted of up to 50 larvae. Prevalence of infection and mean larval burdens declined with increasing age of host. Only one of 258 duodena examined was infected with G. nasalis and this horse originated from the south coast of England, outside of the catchment area of the other horses examined.