Hypoderma spp

From Cow
Hypoderma spp larvae protruding from back in a 2-year-old steer
Hypoderma spp, 3rd stage larva. Courtesy of Dr. Raffaele Roncalli
Hypoderma bovis. Courtesy of Dr. Dietrich Barth, Merial

H bovis and H lineatum (warble flies) are occasional parasitic flies of cattle in North America, Europe, Africa, and Asia, causing stress to cattle and significant economic losses to the cattle industry[1][2].

Adult Hypoderma lay eggs on the hairshaft of cattle, particularly the legs and lower body. The eggs hatch in 3-7 days, and first-stage larvae travel to the base of the hair shaft and penetrate the skin[3]. H lineatum larvae then migrate to the submucosal connective tissue of the esophageal wall, where they accumulate for 2 - 4 months. H bovis larvae migrate to the region of the spinal canal, where they are found in the epidural fat between the dura mater and the periosteum for a similar period[4].

Infestation with warble flies causes 'worry' to cattle. The larvae and their secretions in the epidural fat of the spinal canal are associated with dissolved connective tissue, fat necrosis, and inflammation. Sometimes, the inflammation extends to the periosteum and bone, producing a localized area of periostitis and osteomyelitis. Penetration of the skin by newly hatched larvae may produce a hypodermal rash, most often in older, previously infested cattle.

Larvae migrating to the oesophageal mucosa results in chronic oesophagitis[5].

Diagnosis is based on presenting clinical signs as well as isolation of Hypoderma spp flies and larvae in the skin and dermis.

ELISA assays are also available, but not readily sourced commercially[6].

Treatment against warble flies relies primarily on topical applications such as fipronil, doramectin, ivermectin or moxidectin.

References

  1. Cicek H et al (2011) Prevalence and economic significance of bovine hypodermosis in Afyonkarahisar province of Turkey. Trop Anim Health Prod 43(1):17-20
  2. Hassan MU et al (2010) Bovine hypodermosis - a global aspect. Trop Anim Health Prod 42(8):1615-1625
  3. Vázquez L et al (2012) Antigen-specific antibody isotypes, lymphocyte subsets and cytokine profiles in cattle naturally infested by Hypoderma sp. (Diptera: Oestridae). Vet Parasitol 184(2-4):230-237
  4. Merck Vet Manual
  5. Panadero R et al (2007) Occurrence and larval growth of Hypoderma lineatum in the oesophagi of cattle from northwest Spain: influence of geographical and climatic conditions. Med Vet Entomol 21(3):225-230
  6. Panadero R et al (2007) Evaluation of an antigen capture ELISA for the early diagnosis of Hypoderma lineatum in cattle under field conditions. Vet Parasitol 147(3-4):297-302