Description:

The horse roundworm, an ascarid, is a rigid, heavy-bodied worm up to 50 centimeterslong.

Predilection site: Small intestine.

Geographic distribution : Very common throughout the US.

Life cycle:

P. equorum (ascarid; roundworm) is a common nematode parasite which occurs in the small intestine of immature horses world-wide. Adult female ascarids lay eggs in the small intestine, and these eggs pass into the environment within the feces of the host. The infective stage is a larvated egg (containing a second stage larva [L]3); development requires approximately 10 days at temperatures of 25°C to 35°C . Larvated eggs survive in the environment for up to five or 10 years, and infection is acquired through inadvertent ingestion of eggs. Larvae emerge from eggs within the alimentary tract of a horse, and migrate through the liver and lungs before returning to the small intestine approximately one month later as fourth stage larvae (L4). Ascarids mature progressively in the small intestine and achieve patency about 75 to 80 days after infection
P. equorum is one of the rare nematodes which induces absolute acquired immunity. Most horses become immune during the first year of life, so patent ascarid infections are rarely diagnosed in horses over two years of age.

Causal Agent

Several protozoan species in the genus Entamoeba colonize humans, but not all of them are associated with disease.  Entamoeba histolytica is well recognized as a pathogenic ameba, associated with intestinal and extraintestinal infections.  The other species are important because they may be confused with E. histolytica in diagnostic investigations.

Life cycle of Entamoeba histolytica

Cysts and trophozoites are passed in feces .  Cysts are typically found in formed stool, whereas trophozoites are typically found in diarrheal stool.  Infection by Entamoeba histolytica occurs by ingestion of mature cysts in fecally contaminated food, water, or hands.  Excystation occurs in the small intestine and trophozoites are released, which migrate to the large intestine.  The trophozoites multiply by binary fission and produce cysts , and both stages are passed in the feces .  Because of the protection conferred by their walls, the cysts can survive days to weeks in the external environment and are responsible for transmission.  Trophozoites passed in the stool are rapidly destroyed once outside the body, and if ingested would not survive exposure to the gastric environment.  In many cases, the trophozoites remain confined to the intestinal lumen ( : noninvasive infection) of individuals who are asymptomatic carriers, passing cysts in their stool.  In some patients the trophozoites invade the intestinal mucosa ( : intestinal disease), or, through the bloodstream, extraintestinal sites such as the liver, brain, and lungs ( : extraintestinal disease), with resultant pathologic manifestations.  It has been established that the invasive and noninvasive forms represent two separate species, respectively E. histolytica and E. dispar.  These two species are morphologically indistinguishable unless E. histolytica is observed with ingested red blood cells (erythrophagocystosis).  Transmission can also occur through exposure to fecal matter during sexual contact (in which case not only cysts, but also trophozoites could prove infective).

ادامه مطلب....

Diphyllobothrium latum, the fish tapeworm, is the biggest tapeworm in humans. It causes a parasitic infection called diphyllobothriasis which is acquired by eating raw fish infected with the parasite. Diphyllobothriasis is found in Chile, Peru, Uganda and in the Northern Hemisphere (northern Asia, Europe and America) in areas of rivers and lakes. Diphyllobothrium species include: D. cordatum, D. dalliae, D. dendriticum, D. lanceolatum, D. latum, D. pacificum, D. ursi and D. yonagoensis. Diphyllobothrium latum is the most common and mostly found in Scandinavia, the Baltics and western Russia.

The life cycle of Diphyllobothrium latum starts, when immature eggs are passed in the feces of an infected human. The eggs mature in water within three weeks and form oncospheres. Larvae called coracidia hatch and get eaten by freshwater crustaceans such as copepod. After ingestion coracidia develop into procercoid larvae. If the copepod is eaten by a small fish (second intermediate host), the procercoid larvae penetrate the gut and migrate to muscle tissue where they develop into plerocercoid larvae (sparganum), the infective stage for humans. Usually a third intermediate host is needed because humans do not usually eat raw fish this small. If a trout, walleyed pike or perch eats the smaller fish, the plerocercoid larvae once again penetrate the gut and migrate to fish flesh. If a human eats the infected fish raw or undercooked the plerocercoid larvae develop into adults in the small intestine. The adults attach to the intestinal mucosa with two shallow, bilateral grooves (bothria) of their scolex. The scolex is 3 mm long and 1 mm wide. The long, flat body consists of segments, proglottids, that are produced by the neck. Full grown proglottids are about 10 mm wide and 3 mm long. The segments absorb nutrients and have their own digestive systems. As proglottids mature, they release eggs and eventually break off from the body. A Diphyllobothrium latum proglottid is characterized by a rosette-shaped uterus at its center. The eggs are ellipsoidal or oval measuring 55–75 µm by 40–50 µm. They are passed in the feces unembryonated (immature). From the start of the infection it takes about six weeks for the eggs to appear in the feces. One adult tapeworm can shed up to a million eggs per day. It can grow over 10 meters long and live up to 20 years.

استرتاژیا _ کرم قهوه ایی شیردان

اسپیکولهای قهوه ایی قطور و پررنگ و کوتاه و 2 یا 3 شاخه

شیردان نشتخوارکنندگان

استرونژیلوس ولگاریس _  استرونگل های بزرگ

تشخیص بر اساس ساختار دهان که دارای مجرای پشتی و یک زوج دندان گوشی شکل در کف دهان می باشد

در کولون اسب

اسکرجابینما اویس _ کرم سنجاقی گوسفند

مری در قسمت انتهایی واجد یک بولب متسع و کروی است

روده کور گوسفند و بز

اکسیروس اکوئی

مری در ابتدا پهن بوده سپس باریک می شود و در ادامه حالت بولب پیدا میکند

روده بزرگ تک سمی ها

ادامه مطلب ....

Cryptosporidium

Eimeria spp. (coccidian)

Dictyocaulus vivparus (lungworm)

Muellerius capillaris (goat lung worm)

Fasciola hepatica (liver fluke)

Haemonchus contortus (barber pole worm)

Ostertagia circumcincta (brown stomach worm)

Trichostrongylus spp. (hair worm)

Nematodirus spp (thin-necked intestinal worm)

Oesophagostomum columbianum (nodular worm)

Strongyloides papillosus (common thread worm)

Parelaphostrongylus tenuis (brain or meningeal worm)

Trichuris ovis (whipworm)

Moniezia expansa (tapeworm)