Mesostigmatid mites

Etiology:  Ornithonyssus bacoti (Tropical Rat Mite) is a blood-sucking mite of rats.

Incidence:  Incidence of infection is occasional.

Transmission:  Transmission occurs by direct contact with infected animals or bedding.

Distribution:  These mites can infect the entire rat as well as abide on the bedding in cages and surfaces of racks, and especially crevices or cracks in flooring and walls of room. This mite lives on the rodent only long enough for a blood meal, then drops off the animal until their next blood meal.

Clinical signs:

Ornithonyssus bacoti – Clinical signs include debilitation, anemia, decreased reproductive rate and death. This mite is also a vector of several rickettsial and bacterial pathogens.

Laelaps echidninus – Clinical signs are not usually observed. According to Flynn’s, the mouthparts of Laelaps echnidninus cannot pierce the skin [1].

Diagnosis:  Diagnosis can be made by examining rats, bedding and surrounding areas for blood-engorged mites.

Diagnostic morphology:  Ornithonyssus bacoti: Large tick-like body, often blood engorged. Prominent chelicerae (piercing mouthparts) and abundant body setae (hairs). Three pairs of setae on rectangular sternal plate (photo).

Mesostigmatid mites
Laelaps echidninus: Tick-like body, but more globular, with long stout setae. Three pairs of setae on semi-rectangular sternal plate.

Public Health Significance:  This mite is not host specific and there is zoonotic potential [4].

1.            Flynn’s Parasites of Laboratory Animals. 2 ed. American College of Laboratory Animal Medicine2007, 2121 State Avenue, Ames, Iowa 50014: Blackwell.