EHRLICHIOSIS

EHRLICHIOSIS


Ehrlichiosis is a group of tick-borne diseases that attack white blood cells. It is a seasonal disease that corresponds to the months when ticks are active. In dogs the disease is also known as tracker dog disease, canine hemorrhagic fever, or canine typhus.



MORBIDITY: +




MORTALITY: +




ETIOLOGY: BACTERIAL


Ehrlichia spp. are small, gram-negative, obligate intracellular coccobacilli that cause ehrlichiosis. There are many species that cause disease in various animals, but the zoonotic species are E. chaffeensis, E. ewingii, Anaplasma phagocytophilum (formerly E. equi and E. phagocytophila), and Neorickettsia sennetsu (formerly E. risticii). E. canis may be zoonotic, but confirmation has not been completed. Ehrlichia bacteria must infect white blood cells to multiply. Within the cells, they multiply to form large aggregates called morulae, which are visible on a stained blood smear. The white blood cells are responsible for protection of the body from outside invaders, so damage to these cells and their consequent removal from circulation can make the host more susceptible to developing diseases.



HOST


The host for ehrlichiosis depends on the species of Ehrlichia.



TRANSMISSION


Ixodid (hard) ticks are vectors for ehrlichiosis. The Lone Star tick is the primary vector for E. chaffeensis and E. ewingii. A. phagocytophilum is transmitted by black-legged ticks. The vector for N. sennetsu is unknown. The organisms are transmitted from host to host by tick feedings. Ticks at all stages of the tick life cycle (Appendix 1) can become infected when they feed on an infected host (Figure 15).


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FIGURE 15 Ehrlichiosis.


Rarely, ehrlichiosis has been transmitted via blood transfusions. Direct person-to-person or person-to-animal transmission does not occur.



EHRLICHIOSIS IN ANIMALS


E. chaffeensis has been identified in dogs, coyotes, red foxes, deer, goats, and lemurs. The primary reservoir hosts are deer. E. ewingii causes disease in dogs; dogs are also the primary reservoir hosts. Anaplasma phagocytophilum is found in dogs, horses, deer, bison, elk, rodents, llamas, cats, cattle, sheep, goats, and nonhuman primates. The primary reservoir hosts are deer, elk, and rodents. Neorickettsia sennetsu is still a mystery. It causes a mild disease.


Ehrlichiosis in animals is named by which white blood cells are infected. Monocytic ehrlichiosis is characterized by infection of monocytes and macrophages. If granulocytic white blood cells, primarily neutrophils, are infected, then the disease is granulocytic ehrlichiosis.



DOGS


Monocytic ehrlichiosis and granulocytic ehrlichiosis present similar clinical diseases. The incubation period for monocytic ehrlichiosis is 8 to 20 days; for granulocytic ehrlichiosis, it is 1 to 14 days after a tick bite. Dogs usually present with fever, lethargy, anorexia, swollen lymph nodes, enlarged spleen, and weight loss. They may also develop vomiting, diarrhea, lameness, edema in the hind legs, coughing, difficulty breathing, and discharges from the eyes and nose. The acute phase lasts up to 4 weeks, and many times dogs will recover spontaneously. Some dogs recover clinically but still harbor the bacteria to develop a subclinical disease. During the subclinical phase a dog may remain symptom-free, clear the bacteria from its body, or develop chronic ehrlichiosis. Chronic ehrlichiosis is characterized by anorexia; chronic weight loss; fever; depression; weakness; edema in the hind limbs, scrotum, and tail; bleeding disorders; pale mucous membranes; nose bleeds; blood in the urine; or blood in the feces. Many of these signs are attributable to decreased numbers of not only white blood cells but also red blood cells and platelets. Polyarthritis is seen more often in dogs with granulocytic ehrlichiosis than with monocytic ehrlichiosis.

Related posts:

  1. ABOUT THE DISEASES
  2. CAMPYLOBACTERIOSIS (VIBRIOSIS)
  3. MYCOBACTERIUM INFECTIONS (TUBERCULOSIS)
  4. PSITTACOSIS

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Oct 1, 2016 | Posted by in EXOTIC, WILD, ZOO | Comments Off on EHRLICHIOSIS

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