Dermanyssus gallinae is an 0.6-1 mm long, obligate haematophagous mite of the Dermanyssidae family. The mite does not live on the host and during the day it remains hidden in the environment (in the crevices of walls and floors, in nests, etc.); at night the mite climbs on the host and sucks its blood. When fasting it has a whitish appearance, which becomes red or brownish after the blood meal. In warm seasons the life cycle of the mite is completed in just one week; the cycle stops below 9°C. Four stages are present: larva, protonymph, deutonymph and adult.
The larva is an hexapod which does not eat; the other stages have eight legs and feed on blood; adult males eat only occasionally. The female lays its eggs (up to seven at a time, about thirty in all) in protected places such as cracks and crevices in environments where birds are present. Without the host the parasite can survive for up to eight months without feeding.
EPIDEMIOLOGY
D. gallinae can infest many avian species, both domestic and wild, and can also be found in mammals (including in dogs, cats, rabbits and rodents). The mite may also complete its life cycle on human hosts, in whom it causes localized dermatitis. The species is extremely contagious and spreads rapidly in environments in which more birds are present. It can spread through indirect contact (including via wild birds) and via dispersion of the mites.
PATHOGENESIS
The parasite causes itching, emaciation and anaemia, even death, especially in younger patients. Young birds may die while still in their nest. D. gallinae is able to transmit viruses, including the avian pox virus and the Newcastle disease virus, as well as bacteria such as Pasteurella multocida, Salmonella enteritidis, S. gallinarum, Coxiella burnetii, Erysipelothrix rhusiopathiae and Borrelia anserina.
SIGNS AND SYMPTOMS
Birds infested with D. gallinae may exhibit pallor, restlessness, itching, feather picking and stress. During the day no parasites are present; the parasites may be identified at night when they feed, every 2-4 days, staying on the host for around an hour.
DIAGNOSIS
Direct examination of the birds not always allows mite detection, while the mites are usually abundant in the surrounding environment. Double-sided adhesive tape may be placed around the cages as a "trap" for mites, examining it the next day.
THERAPY
D. gallinae is a difficult parasite to eradicate; numerous and periodic environmental treatments are necessary, first eliminating any possible refuge for the parasites and then spraying a pyrethrum compound with residual effect. Resistance to the products used is often reported. Temperatures above 45°C are effective in killing the mites.
For bird treatment a pyrethrum spray may be used, or topical applications of ivermectin, selamectin or moxidectin.
Treatments limited to only the animals are not effective.
PREVENTION
The best prevention consists in introducing into the environment birds which have been carefully examined, treated preventively and subjected to a quarantine period in a room separate from the other animals.
Suggested reading
- George DL et al. Should the poultry red mite Dermanyssus gallinae be of wider concern for veterinary and medical science? Parasit Vectors 2015;8(0):178.
- Sparagano O, George D, Harrington D, Giangaspero A. Significance and control of the poultry red mite, Dermanyssus gallinae. Annual Review of Entomology 2014;59:447-466.
- Todisco G, Paoletti B, Giammarino A, Manera M, Sparagano OAE, Iorio R, Giannella B, Robbe D.Comparing therapeutic efficacy between ivermectin, selamectin, and moxidectin in canaries during natural infection with Dermanyssus gallinae. Ann N Y Acad Sci. December 2008;1149(0):365-7.
- http://entnemdept.ufl.edu/creatures/livestock/poultry/chicken_mite.htm
- http://parasitipedia.net/index.php?option=com_content&view=article&id=2540&Itemid=2816