Dirofilaria tenuis
| Dirofilaria tenuis | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Secernentea |
| Order: | Spirurida |
| Family: | Onchocercidae |
| Genus: | Dirofilaria |
| Species: | D. tenuis |
| Binomial name | |
|
Dirofilaria tenuis Chandler, 1942 |
|
Dirofilaria tenuis is a species of nematode, a parasitic roundworm that infects the subcutaneous tissue of vertebrates.D. tenuis most commonly infects raccoons, but some human cases have been reported They are vectored by mosquitoes and follow similar development and transmission patterns as other Dirofilaria.
Adults of D. tenuis are long and thin with a pointed anterior end. The posterior end is long, drawn out, and typically remains coiled. It possesses a hook and may have up to fifteen pairs of sensory organs known as papillae covering the posterior region of the body. Females vary in length, from 8–13 cm, averaging about 9 cm, while males are 4-4.8 cm in length, averaging 4.5 cm. D. tenuis possess eight papillae in addition to two amphids around the mouth opening. The mouth leads to a short esophagus, which is connected to the intestine and leads to the excretory opening. D. tenuis also possesses a nerve cord at the anterior end of the body cavity and differentiated reproductive organs. The outermost surface of the cuticle, or outer covering of the worm, is covered in small lines running transversely and more prominent ridges arranged longitudinally. These ridges are less prominent at the head and anal ends. The combination of the transverse lines and longitudinal ridges can give D. tenuis a beaded appearance.
D. tenuis is introduced to the host (either a raccoon or, as in some rare cases, a human) as a larva when the vector, most commonly an Aedes or Anopheles mosquito, takes a blood meal and the parasite enters the host through the bite wound. Once inside the host, the larva molts into its final larval stage and then into an adult. As an adult it resides in the subcutaneous tissue of the host. These adults are able to live up to ten years within the tissue of the host. The female is able to reproduce throughout her entire adult life and her eggs and microfilariae enter the peripheral blood stream of the host. They are then ingested by the vector mosquitoes during a blood meal and travel to the malphigian tubules of the mosquito. There, they undergo development, from microfilaria, to first, second, and finally third stage larvae. This typically spans a length of 10–12 days. Following the third larval stage, at which point they have become infective, they travel back to the proboscis of the mosquito via the haemocoel and enter another definitive host. If the mosquito is highly infected, multiple larvae can be transmitted in one blood meal. Humans are a dead-end host for D. tenuis; after the larva molts into an adult, it cannot reproduce. The worm may live subcutaneously for several months before it dies.
...
Wikipedia