Neorickettsia

A genus of bacteria in the family Anaplasmataceae

Neorickettsia is a genus of obligate intracellular bacteria belonging to the family Anaplasmataceae. These bacteria are known to infect a variety of hosts, including mammals, birds, and fish, and are transmitted by trematodes (flukes). Neorickettsia species are responsible for several diseases in animals, most notably Potomac horse fever in horses and salmon poisoning disease in dogs.

Taxonomy

The genus Neorickettsia is part of the order Rickettsiales, which includes other genera such as Rickettsia and Ehrlichia. Neorickettsia species are closely related to other members of the Anaplasmataceae family, sharing similar morphological and genetic characteristics.

Species

The genus Neorickettsia includes several species, with the most notable being:

• Neorickettsia risticii, the causative agent of Potomac horse fever.
• Neorickettsia helminthoeca, responsible for salmon poisoning disease in dogs.
• Neorickettsia sennetsu, which causes Sennetsu fever in humans.

Morphology and Physiology

Neorickettsia are small, gram-negative bacteria that reside within the cytoplasm of host cells. They are pleomorphic, meaning they can vary in shape and size, and are typically coccoid or rod-shaped. As obligate intracellular organisms, they rely on their host cells for nutrients and energy, making them difficult to culture outside of a living host.

Transmission

Neorickettsia species are transmitted through the ingestion of infected trematodes. These trematodes have complex life cycles involving multiple hosts, including snails, fish, and mammals. For example, in the case of Potomac horse fever, horses become infected by ingesting aquatic insects that have consumed infected trematodes.

Pathogenesis

Once inside the host, Neorickettsia bacteria invade and multiply within monocytes and macrophages, leading to systemic infection. The clinical manifestations of Neorickettsia infections vary depending on the species and host, but common symptoms include fever, lethargy, anorexia, and gastrointestinal disturbances.

Diagnosis

Diagnosis of Neorickettsia infections typically involves a combination of clinical signs, serological tests, and molecular techniques such as polymerase chain reaction (PCR) to detect bacterial DNA in blood or tissue samples.

Treatment

Treatment of Neorickettsia infections often involves the use of antibiotics such as tetracycline or doxycycline. Supportive care, including fluid therapy and anti-inflammatory medications, may also be necessary to manage symptoms and complications.

Prevention

Preventive measures focus on reducing exposure to infected trematodes. This can include controlling snail populations in aquatic environments and preventing animals from consuming raw or undercooked fish.

Also see

• Rickettsiales
• Anaplasmataceae
• Potomac horse fever
• Salmon poisoning disease
• Obligate intracellular parasite

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