Histomoniasis is caused by a protozoan that infects the ceca, and later the liver, of turkeys, chickens, and occasionally other galliform birds. In turkeys, most infections are fatal; in other birds, mortality is less common.
Etiology:
The protozoan parasite Histomonas meleagridis is transmitted most often in embryonated eggs of the cecal nematode Heterakis gallinarum , and sometimes directly by contact with infected birds. Outbreaks spread quickly through flocks by direct contact. A large percentage of chickens harbor this worm, and histomonads have been located in adult worms of both sexes. Three species of earthworms can harbor H gallinarum larvae containing H meleagridis , which are infective to both chickens and turkeys. H meleagridis survives for long periods within Heterakis eggs, which are resistant and may remain viable in the soil for years. Histomonads are released from Heterakis larvae in the ceca a few days after entry of the nematode and replicate rapidly in cecal tissues. The parasites migrate into the submucosa and muscularis mucosae and cause extensive and severe necrosis. Histomonads reach the liver either by the vascular system or via the peritoneal cavity, and rounded necrotic lesions quickly appear on the liver surface. Histomonads interact with other gut organisms, such as bacteria and coccidia, and depend on these for full virulence.

 

Anal sac disease is the most common disease entity of the anal region in dogs. Small breeds are predisposed; large or giant breeds are rarely affected. In cats , the most common form of anal sac disease is impaction.

Etiology and Pathogenesis:
Anal sacs may become impacted, infected, abscessed, or neoplastic. Failure of the sacs to express during defecation, poor muscle tone in obese dogs, and generalized seborrhea (which produces glandular hypersecretion) lead to retention of sac contents. Such retention may predispose to bacterial overgrowth, infection, and inflammation.

Anal gland disease is a common problem in cats and dogs. The anal glands, also called 'anal sacs,' can become impacted, infected, and abscessed. Affected pets may lick the anal area, 'scoot' along the floor, or have problems with defecation.

Location and function of anal glands
As the cat is viewed from behind, anal glands (also called anal sacs) are located on each side of and slightly below the anal opening, at the 4 o'clock and 8 o'clock positions. A tiny duct or tube leads under the skin to an opening directly beside the anus.

Infectious canine hepatitis (ICH) is a worldwide, contagious disease of dogs with signs that vary from a slight fever and congestion of the mucous membranes to severe depression, marked leukopenia, and prolonged bleeding time. It also is seen in foxes, wolves, coyotes, and bears; other carnivores may become infected without developing clinical illness. In recent years, the disease has become uncommon in areas where routine immunization is used.