Trichinella spiralis is a nematode parasite, occurring in rats, pigs, and humans, and is responsible for the disease trichinosis. It is sometimes referred to as the "pork worm" due to it being found commonly in pork or rat products that are undercooked.Trichinella species are the smallest nematode parasite of human, which has an unusual life cycle and one of the most widespread and clinically important parasites in the world. The small adult worms mature in the intestine of an intermediate host such as a pig. Each adult female produces batches of live larvae, which bore through the intestinal wall, enter the blood (to feed on it) and lymphatic system, and are carried tostriated muscle Once in the muscle, they encyst, or become enclosed in a capsule. Humans can be infected by eating infected pork or wildcarnivores such as fox, cat or bear.
Tuesday, July 27, 2010
Trichinella spiralis
Trichinella spiralis is a nematode parasite, occurring in rats, pigs, and humans, and is responsible for the disease trichinosis. It is sometimes referred to as the "pork worm" due to it being found commonly in pork or rat products that are undercooked.Trichinella species are the smallest nematode parasite of human, which has an unusual life cycle and one of the most widespread and clinically important parasites in the world. The small adult worms mature in the intestine of an intermediate host such as a pig. Each adult female produces batches of live larvae, which bore through the intestinal wall, enter the blood (to feed on it) and lymphatic system, and are carried tostriated muscle Once in the muscle, they encyst, or become enclosed in a capsule. Humans can be infected by eating infected pork or wildcarnivores such as fox, cat or bear.
Wednesday, July 21, 2010
Naegleria fowleri
Naegleria fowleri is a "brain eating" amaeba, free-living excavate form of protist typically found in warm bodies of fresh water, such as ponds, lakes, rivers, and hot springs. It is also found in soil, near warm water discharges of industrial plants, and minimally chlorinated swimming pools, (there is no evidence of this amoeba living in ocean water) in an amoeboid or temporary flagellate stage.
LIFECYCLE
Naegleria fowleri exists in nature in three forms: a flagellate, an ameboid and a cyst.
Flagellate stage: A biflagellate form occurring when trophozites are exposed to a change in ionic concentration such as placement in distilled water. The transformation of trophozoites to flagellate form occurs within a few minutes.
Trophozoite stage: The reproductive stage of the protozoan organism, which grows fastest at around 42°C and proliferates by binary fission. In their free-living state, trophozoites feed on bacteria. In tissues, trophozoites phagocytize red blood cells and white blood cells and destroy tissue.
It is found worldwide, most commonly, in:
- Warm bodies of fresh water, such as lakes, rivers
- Geothermal water such as hot springs
- Warm water discharge from industrial plants
- Minimally chlorinated swimming pools
- Soil
Wuchereria Bancrofti
Wuchereria bancrofti or Filaria, is a parasitic filarial nematode worm spread by a mosquito vector. It is one of the three parasites that cause lymphatic filariasis, an infection of the lymphatic system by filarial worms. It affects over 120 million people, primarily in Africa, South America, and other tropical and sub-tropical countries
W. bancrofti largely affects areas across the broad equatorial belt (Africa, the Nile Delta, Turkey, India, the East Indies, Southeast Asia, Philippines, Oceanic Islands, Australia, and parts of South America.)
The mosquito vectors of W. bancrofti have a preference for human blood and it appears that humans are the only animals naturally infected with W. bancrofti. There is no reservoir host.
Ascaris lumbricoides
Ascaris lumbricoides is the giant roundworm of humans, belonging to the phylum Nematoda. An ascarid nematode, it is responsible for the disease ascariasis in humans, and it is the largest and most common parasitic worm in humans. A quarter of the human population is estimated to be infected by this parasite. Ascariasis is prevalent worldwide and more so in tropical and subtropical countries.Ascaris lumbricoides, or "roundworm", infections in humans occur when an ingested infective egg releases a larval worm that penetrates the wall of the duodenum and enters the blood stream. From here, it is carried to the liver and heart, and enters pulmonary circulation to break free in the alveoli, where it grows and molts. In 3 weeks, the larvae pass from the respiratory system to be coughed up, swallowed, and thus returned to the small intestine, where they mature to adult male and female worms. Fertilization can now occur and the female produces as many as 200,000 eggs per day for a year. These fertilized eggs become infectious after 2 weeks in soil; they can persist in soil for 10 years or more.
The eggs have a lipid layer, containing ascarocides and it makes them resistant to the effects of acids and alkalis as well as other unpleasant chemicals. This resilience helps to explain why this nematode is such a ubiquitous parasite.
Most diagnoses are made by identifying the appearance of the worm or eggs in feces. Due to the large quantity of eggs laid physicians can diagnose using only one or two fecal smears.
Infections can be treated with drugs called ascaricides. The treatment of choice is Mebendazole. The drug functions by binding to tubulin in the worms' intestinal cells and body wall muscles. Nitazoxanide and ivermectin can also be used.
Schistosoma mansoni
Schistosoma mansoni is a significant parasite of humans, a trematode that is one of the major agents of the disease schistosomiasis. The schistosomiasis caused by Schistosoma mansoni is intestinal schistosomiasis.
Schistosomes are atypical trematodes in that the adult stages have two sexes (dioecious) and are located in blood vessels of the definitive host. Most other trematodes are hermaphroditic and are found in the intestinal tract or in organs, such as the liver. The lifecycle of schistosomes includes two hosts: a definitive host (i.e. human) where the parasite undergoes sexual reproduction, and a single intermediate snail host where there are a number of asexual reproductive stages.