User:Amanor1/Capillariahepatica

Capillaria hepatica is a nematode roundworm from the family Trichinellidae that infects the liver. In humans it causes Hepatic capillariasis, however it mostly infects the liver of rodents.

Distribution
Rare cases of human infections with C. hepatica have been reported in temperate and tropical zones and on all of the continents, with the exception of Australia. There are no endemic areas of infection with Capillaria hepatica and human infection primarily results from Zoonotic transmission.

Morphology
Adult worms take the shape of a slender nematode, with the anterior part of the body narrow and the posterior part gradually swelling. The females measure about 53-78mm x 0.11-0.20mm, but the males are approximately 24-37mm x 0.07-0.10mm. The adult worms are rarely seen intact, as they mature and die in the Parenchyma of the liver. The adult females lay eggs that are about 48-66μm x 28-36μm. The shell of the eggs is striated with shallow polar prominences at either end. Numerous mini-pores can be seen in the outer shell as well. Unembryonated eggs may be ingested by a carnivore, in which case they are harmless and pass out in the feces. Eggs will embryonate in the environment, where they require air and damp soil to become infective. Under optimal conditions this takes about 30 days. Larvae are juvenile versions of the adult worm.

Host and Tissue Niche
This parasite is Monoxenous, requiring only one host to complete its life cycle. The hosts are usually rodents, but may be also be pigs, carnivores, primates and humans. The tissue Niche of this parasite is the liver. The adult females will deposit eggs in the Parenchyma of the liver. Occasionally in humans larvae will migrate to the lungs, kidneys and other organs.

Life Cycle
Adult nematodes will invade the host liver and undergo sexual reproduction, laying hundreds of eggs in the surrounding Parenchyma. The eggs are not passed in the feces of the host and will remain in the liver until the animal dies and decomposes, or is eaten by a predator or scavenger. Eggs ingested by such an animal are unembryonated, are not infectious and are passed in the feces. Eggs embryonate in the environment from death/decomposition of host or predator and the cycle continues when embryonated eggs are eaten by a suitable mammalian host. After becoming consumed, infective eggs hatch in the intestine, releasing larvae. The larvae migrate via the portal vein to the liver. Larvae take about four weeks to mature into adults and mate in the liver. Humans are usually infected after ingesting embryonated eggs in fecal-contaminated food, water, or soil.

Pathogenesis and Survival in Host
In humans C. hepatica causes Hepatic capillariasis, a serious liver disorder. The nematode wanders through the host liver causing loss of liver cells and thereby loss of function. The worms, however, are eventually killed by the host Inflammatory response, leaving the eggs behind. The eggs can become encased by Granulomatous tissue and large sections of the Parenchyma may be replaced by these egg masses. Capillaria hepatica can also cause Hepatomegaly. Infections of C. hepatica can present with several clinical symptoms including, abdominal pain in the liver area, weight loss, decreased appetite, fever and chills. This parasite can be fatal in humans, as transmission and survival of the parasite depend on death of the definitive host in order for the eggs to reach soil and water to embryonate.

Diagnosis
The specific diagnosis of Capillaria hepatica infection is based on demonstrating the adult worms and/or eggs in liver tissue at biopsy or Necropsy. Key identification features of this parasite are a striated shell and shallow polar prominences of the egg and a narrowing at anterior end and gradual swelling at posterior end of the adult worm. Identification of C. hepatica eggs in the stool does not result from infection of the human host, but from ingestion by that host of livers from infected animals, the eggs will then pass out harmlessly in the feces. Most cases have been determined after death because clinical symptoms resemble those of numerous liver disorders.

Treatment and Prevention
The drug of choice for treating Capillaria hepatica infections is mebendazole, with albendazole as an alternative. Albendazole must be taken with food because a fatty meal with increase the Bioavailability of the drug. Two ways of preventing C. hepatica infections in humans would be to institute effective rodent control programs and preventing dogs and cats from eating rodents.

Global Impacts
The selective liver damage done by Capillaria hepatica in rodents has been used to study the Regeneration capabilities of the mammalian liver and for testing Antifibrotic drugs. There is also some potential as a biological control agent for rodent populations