(1/8) Durably controlling bovine hypodermosis.
Cattle hypodermosis, due to insect larvae, is widely spread over the northern hemisphere. Very efficient insecticides are available and their use in most countries are done on an individual level but never cover the whole cattle population of a country. Untreated animals remain the reservoir of the disease and annually re-infest the cattle population. The economic effects of this disease on animal production (meat, milk and the leather industry) but also on the general cattle health status, have led many European countries to launch organised control programs. The first example of definitive hypodermosis control goes back one hundred years ago when Danish farmers eradicated hypodermosis from the Danish islands by manual elimination of the warbles. Since then, more and more European countries have considered the feasibility and economic returns of such programs. The various factors which foster these programs are related to (i) biological factors, (parasite cattle specificity, synchronous biological cycles of both species of insects involved), (ii) the development of more and more efficient insecticides used only once a year by systemic application, with high efficiency at very low dosages against the first larval stage of Hypoderma spp., (iii) the development of acute techniques of detection of the disease for the monitoring of hypodermosis free countries and (iv) the durable successful results obtained in more and more European countries. Although the programs were imposed by different partners of the livestock channel production (farmers, dairy industry, leather industry) and have been engaged within the last 50 years in many European countries (Denmark, The Netherlands, Ireland, the United Kingdom, the Czech Republic, Germany, France and Switzerland) common features have emerged among these different eradication programs. They all need a preliminary statement of the economic impact of this pest and the farmers' awareness of the economic returns of such programs. The programs' efficacy depends: (i) on a good knowledge ofthe epidemiology of the parasites, (ii) on the simultaneous implementation of the control program on the whole national cattle population whatever the structure monitoring the treatments (veterinary services, farmers association), (iii) on a national Warble fly legislation making the treatments compulsory and (iv) on an acute epidemiological survey as soon as the status of a hypodermosis free country is reached and the treatments are suspended. The sanitary and financial returns of such programs are a benefit to all the partners of livestock production, to the quality of the environment and to the consumers. (+info)
(2/8) Migration of warble fly larvae in the yak and optimum timing of ivermectin treatment.
Sixty yaks were autopsied to determine the migration pattern of warble fly larvae. In August, first instars were observed in the body of yak for the first time. These larvae peaked in number in October. From November to February, second instars were detected and their number peaked in January. Third instars appeared in January and peaked in March. Forty-five yaks were administered with ivermectin: 15 animals in September, 15 in October and 15 in November. Between December and June, the number of warbles was checked by palpation. Although some warbles were observed in the September- and November-treated groups, no warbles were detected in the October-treated group. Treatment of yaks with ivermectin was most effective for warble fly in October. (+info)
(3/8) Ophthalmomyiasis caused by the reindeer warble fly larva.
Two boys with ophthalmomyiasis caused by the first instar larva of the reindeer warble fly Hypoderma tarandi are reported. Both were 9 years old and came from the coast of northern Norway. One had ophthalmomyiasis interna posterior and one eye had been removed because of progressive pain and blindness. Histological examination showed the remains of a fly larva. The second boy had ophthalmomyiasis externa with a tumour in the upper eyelid, and histological examination showed a warble with a well preserved larva. Identification of the parasite in the histological material was based on the finding of cuticular spines and parts of the cephalopharyngeal skeleton identical with those of the first instar larva of H tarandi. (+info)
(4/8) The efficacy of eprinomectin extended-release injection against Hypoderma spp. (Diptera: Oestridae) in cattle.
(5/8) An intradermal test to detect latent warble (Hypoderma spp.) infection in cattle.
An intradermal test was developed to screen cattle for infection with the first-instar larvae of the warble flies Hypoderma lineatum and H. bovis. The diagnostic antigen, prepared from the first-instar larvae of H. lineatum, produced a distinct dermal reaction in cattle infected with the first-instar larvae of either species, but not in cattle in which the infection could not be confirmed later either on necropsy or by the appearance of warbles in the back. The reaction to the antigen was unpredictable in cattle with warbles in their backs. The diagnostic property of the antigen was also demonstrated in rabbits and guinea pigs artificially sensitized to the antigen. (+info)
(6/8) Systemic control of cattle grubs (Hypoderma spp.) in steers treated with Warbex and weight gains associated with grub control.
When applied to yearling steers on November 30, pour-on applications of famphur at 40 or 50 mg/kg were unsatisfactory for systemic grub control as they only reduced the number of warble grubs by 52.2 and 68.4%, respectively. The treatments, which had no adverse effects on the health of steers or cellular constituents of their blood, reduced the whole-blood cholinesterase, with the maximum reduction occurring 15 days after treatment. Low ambient temperatures prevailing at the time of treatment and during the two following weeks might have impeded the absorption of famphur through the skin and reduced its effectiveness for grub control. With the grub damage kept to the minimum by weekly manual removal of warble grubs, the groups treated with famphur at 40 or 50 mg/kg outgained (P less than 0.05) the untreated group by 29.9 and 13.4 kg/steer, respectively, during the posttreatment period of 181 days. These results indicate the economic benefits of grub control. (+info)
(7/8) Effect of the parasite enzyme, hypodermin A, on bovine lymphocyte proliferation and interleukin-2 production via the prostaglandin pathway.
The immune function of cattle infected with a primary infestation of Hypoderma lineatum is impaired during the first instar migration of the larvae. Hypodermin A (HA) is an enzyme secreted by the larvae that is implicated in immunosuppression. The response of bovine peripheral blood mononuclear cells (PBMC) to HA was examined in this study. HA blocked their proliferation in response to phytohaemagglutinin (PHA) and its effect was enhanced when cells were preincubated with HA before activation. This suggests that HA affects the lymphocyte commitment to blastogenesis during the early stages of their activation. HA also markly reduced the production of interleukin-2 (IL-2) in PHA-stimulated bovine PBMC cultures. Furthermore, indomethacin, which inhibits prostaglandin (PG) synthesis, blocked the immunosuppressive effect of HA on the PBMC proliferative response. The concentration of PGE2 in medium of PBMC or PMA-stimulated monocyte cultures was increased by incubation with HA. Thus, the HA appeared to act by reducing IL-2 production via a prostaglandin-dependent pathway. (+info)
(8/8) Eosinophilic mediastinitis, myositis, pleuritis, and pneumonia of cattle associated with migration of first-instar larvae of Hypoderma lineatum.
Migrating first-instar larvae of Hypoderma lineatum are a frequent cause of focal inflammatory lesions in connective tissues of the mediastinum, parietal and visceral pleura, peritoneum, lungs, diaphragm, and other loci. The lesions are characterized grossly by foci of yellowish or greenish gelatinous edema and microscopically by infiltration of the edematous tissue by a dense array of eosinophils. Lesions were recognized during a period of several weeks in late spring; the timing was attributable to events in the life cycle of the fly. The larvae, which were small (approximately 1 x 4.5 mm), transparent, and unobtrusive, were recovered from lesions in 12 of 20 cattle in which careful parasitologic examination was made. (+info)