Treatment and control of bovine hypodermosis with ivermectin long-acting injection (IVOMEC® GOLD).

BACKGROUND: The studies reported here were conducted to assess the efficacy of ivermectin long-acting injection (IVM LAI; IVOMEC® GOLD, Merial; 3.15 % w/v ivermectin) for the treatment and control of natural infestations of cattle by Hypoderma bovis and Hypoderma lineatum, which are the most economically important oestrid flies of cattle in the northern hemisphere. METHODS: Cattle selected from herds with a history of Hypoderma infestation were grouped into blocks of three (Italy, 33 cattle; Germany, 30 cattle) or two (USA, 16 cattle) animals each, on the basis of positivity at the pre-treatment anti-Hypoderma antibody titres. Within each block, animals were randomly allocated to one of the following treatment regimens: saline (control); IVM LAI, administered at the predicted time of occurrence of first-instar larvae (Italy, Germany, USA); IVM LAI, administered at the predicted time of occurrence of second- and/or third-instar larvae (Italy, Germany). All treatments were administered by subcutaneous injection in correspondence of the area anterior to the shoulder at 1 ml/50 kg body weight, which corresponds to 630 mcg IVM/kg for IVM LAI. RESULTS: No Hypoderma larvae emerged from animals treated with IVM LAI, whereas live H. lineatum (Italy) or H. bovis (Germany, USA) larvae were collected from saline-treated animals (P < 0.01). No adverse reactions to treatments were in any of the animals enrolled in the study. CONCLUSIONS: The results from this study demonstrate that ivermectin in a long-acting formulation is 100 % efficacious in the treatment of cattle naturally infested by H. bovis and H. lineatum larvae at all stages of development. IVM LAI can, therefore, be used as 'prophylactic' treatment for Hypoderma spp. infestations in absence of external evidence of their presence and thus prior to skin and carcass damage, and as 'therapeutic' treatment, when warbles are already present.

Myiasis due to Hypoderma lineatum infection mimicking the hypereosinophilic syndrome.

Myiasis is the infestation of live humans with larvae of Diptera (true flies). This report describes a protracted illness caused by infestation with Hypoderma lineatum, resembling the hypereosinophilic syndrome. A 35-year-old man had a 9-month multisystemic illness with pronounced eosinophilia, pleuritis, pericarditis, and myositis. Treatments including glucocorticoids did not alter the disease. Diagnostic studies included computed tomography, 2-dimensional echocardiography, leukocyte count, surgical biopsy of skin and muscle, blood immunoglobulin levels, and blood chemistry. Myiasis was recognized when a worm emerged from the patient's skin; after a second worm emerged, the patient's symptoms disappeared rapidly. Other determinations included IgE and IgG levels specific for H lineatum, Western blot, and immunofluorescence for eosinophil major basic protein; IgG antibodies to H lineatum decreased after emergence of the worms. The patient's symptoms mimicked the hypereosinophilic syndrome but resolved when the myiasis became apparent. Specific serologic analyses can identify infected patients, and ivermectin may be useful as treatment.

Efficacy of a pour-on formulation of doramectin against lice, mites, and grubs of cattle.

OBJECTIVE: To determine effectiveness of a pour-on formulation of doramectin against Damalinia bovis, Haematopinus eurysternus, Linognathus vituli, Solenopotes capillatus, Chorioptes bovis, Sarcoptes scabiei, Hypoderma bovis, and Hypoderma lineatum. ANIMALS: Cattle of various ages with naturally acquired or artificial infestations with 1 or more species of lice, mites, or grubs. PROCEDURE: In 10 louse and 6 mite studies, cattle were treated with doramectin (500 microg/kg, topically) on day 0, and parasite counts were performed approximately weekly from days 0 to 35. In 6 grub studies, cattle expected to harbor Hypoderma spp were treated before emergence of warbles. After warbles began to emerge, they were counted every 2 weeks, and grubs were collected and identified by species. RESULTS: Burdens of D bovis, H eurystemus, L vituli, and S capillatus on doramectin-treated cattle were 0 by 28 days after treatment. Burdens of C bovis and S scabiei decreased to 0 in naturally infested cattle and approximately 0 in artificially infested cattle by day 14 to 15. In grub studies, 107 of 136 control cattle had warbles, whereas 2 of 136 doramectin-treated cattle had 1 warble each, which represented a cure rate of 98.5%. CONCLUSION AND CLINICAL RELEVANCE: One topical application of doramectin was highly efficacious against common species of lice, mites, and grubs known to affect performance, health, and appearance of cattle.

Doramectin systemic activity against cattle grubs, Hypoderma lineatum and H. bovis (Diptera: Oestridae), and cattle lice, bovicola bovis (Mallophaga: Trichodectidae), Linognathus vituli and Solenopotes capillatus (Anoplura: Linognathidae), and Haematopinus eurysternus (Anoplura: Haematopinidae), in Wyoming.

Seven individual trials were conducted in Wyoming to evaluate the therapeutic efficacy of doramectin administered subcutaneously at a dosage of 200 micrograms kg-1 against multiple, natural infestations of cattle grubs or cattle lice. Insect species present and the number of trials that included each species were: Hypoderma lineatum, 2; Hypoderma bovis. 1; Bovicola bovis, 5; Haematopinus eurysternus, 1; Linognathus vituli, 5; and Solenopotes capillatus, 3. Examinations for lice were performed prior to treatment and either weekly or bi-weekly thereafter for 28 days. Examinations for cattle warbles were performed either weekly or every 4 to 5 weeks from time of first appearance through last appearance in the backs of the cattle. No H. lineatum, H. bovis, H. eurysternus, L. vituli, or S. capillatus were found on doramectin-treated animals at any time following treatment. By 28 days following treatment, the number of B. bovis was reduced between 58 and 98%. Treatments applied later in the season, i.e. in March, were more efficacious against B. bovis than those applied in January or February.