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Dracunculus insignis
The parasite Dracunculus insignis (taxonomic name Nematoda Phasmidea Camallanata Dracunculus insignis) is a specific type of Guinea worm species. Insignis is a mammal infecting parasite that usually infects semi-aquatic mammals such as opossums, raccoons, and muskrats. D. insignis’s cousin D. medinesis may use humans as the definitive host, but D. insignis does not. Insignis is an important species because it can infect domesticated animals. The pathologies of an infected canine are similar to that of a D. medinesis in a human.

Species Characteristics
Dracunculus insignis is a white round worm as an adult. The average length of this worm is from 17.9-23 centimeters but some of the adults can reach 30 centimeters in length with the females being considerably larger than the males. Both the males and females have characteristic atrophied intestines. The females also have atrophied vulva and vagina. When observing this species, it is easy to determine the gravid females because they are filled with a uterus that is swollen with larvae. Insignis is also composed of longitudinal muscles that are arranged in an oblique array along the body wall.

Guinea worms are an aquatic parasite species that requires water for their life cycles. It is the same case with this specific species. Insignis is found in aquatic areas (e.g. rivers, marshes, bogs, lakes, temporary pools etc.) in both temperate and tropical habitats. The known cases of Insignis infections (in both wildlife and domestic animals) have occurred all over the United States and parts of Canada.

A key feature of Insignis is that it produces a subcutaneous inflammation or swelling generally on the lower limbs/legs, but these swellings can occur on other areas of the body. These swellings can be very painful, but this is not always the case.

Life Cycle
The overall life cycle of D. insignis requires at least two hosts and water. The definitive host is a mammal, generally a semi-aquatic mammal or sometimes a domesticated dog or cat. The definitive host becomes infected by ingesting an infected copepod, the intermediate host. After the larvae (within the copepod) are ingested, they migrate to subcutaneous muscles. It is here that the larvae mature and mate. The females, after mating, move to the lower limbs and become gravid. It is here that the female creates a swelling close to the skin so that when it comes in contact with water the swelling will burst, and the female will release a large number of larvae, called L1 larvae. These larvae are consumed by copepods in the water where they then develop into their infective third larval stage. At this point the L3 larvae can be either consumed by the definitive host, or they can be consumed by a paratenic host such as fish, frogs, or tadpoles, The paratenic host is just another option of transport for the parasite to enter the definitive host.

The development of the parasite within the copepod (to the L3 stage) is dependent on temperature. If the temperature is too low, no growth will occur. The temperature must be 24°C (75°F) for the molt to occur and the larvae to enter the L3 stage. A full complete life cycle takes 10-14 months.

Disease/Pathology
When D. insignis infects the definitive host, it causes some pathology, but it is not life threatening. An infection by D. insignis is called dracunculiasis. There are no symptoms in the beginning of the infection, but once the female has matured and mated she releases a toxin that causes inflammation and this inflammation causes a blister to form on the skin. These blisters almost always appear on the lower limbs/legs. After the blister makes contact with water and bursts, it will result as a scar on the leg. Besides the blisters, a host can experience itchiness, pain from the blisters, and a mild fever. D. insignis cases are fairly common in wildlife. In some areas during springtime, the prevalence of insignis in raccoons can exceed 50%. Cases in domesticated dogs are uncommon and very rare in cats. Diagnosis of dracunculiasis can only occur by examining the females, because the males are almost never seen and do not exit the host like the females will do.

Treatment
Treatment of a D. insignis infection involves a surgical and an anthelmintic compound approach. The surgery is used to remove all of the female worms visible and then this is followed by treatment with the anthelmintic compound. The commonly used compounds are diethylcarbamazine, albendazole, ivermectin and, fenbendazole. The method of winding the worm on a stick with gentle pulling pressure can also be used to remove the parasite.

Infection Developments
In recent years there has been a widening of the species that D. insignis can infect. Insignis used to be thought of as a racoon parasite, but that is no longer the case. In a 2014 article, the Journal of Feline Medicine and Surgery documented its first two cases of cats infected by Insignis. Experimental studies have also shown that primates can also be infected by this parasite as well. The test subject was a rhesus monkey. Seeing this branching out of species that can be infected by D. insignis could possibly mean that this parasite could become zoonotic.