Infectious and non-infectious hemolymphatic diseases generally present with the same clinical symptoms due to cardiovascular
insult, lack of tissue oxygenation and possible impending cardiovascular collapse. Frequently, bacterial sepsis is hard to
differentiate from viral diseases. Endotoxemia due to gastrointestinal infections is always a crucial rule out. When red blood
cell destruction occurs with these diseases, then clinical signs of primary anemia may be the overriding clinical presentation.
General clinical signs will include mucous membrane pallor, possible deposition of pigment in mucous membranes, tachycardia,
tachypnea, weakness, systolic murmur, exercise intolerance, collapse, blindness, ileus, laminitis, and evidence of renal failure.
It is important to determine if anemia is present if there is intravascular or extravascular destruction (Figure 1). A second
issue is identification of primary vasculitis as a syndrome. Identification of vasculitis is further complicated by whether
or not a cellulitis is present as opposed to a vasculitis (Table 1). Third, the clinical diagnosis is frequently confused
by whether or not there is primary red blood cell destruction, platelet destruction, or both.
Equine Granulocytic Ehrlichiosis
Table 1. Most Common Identified Infectious Causes of vasculitis and cellulitis
Equine granulocytic ehrlichiosis caused by Anaplasma phagocytophilum (syn. Ehrlichia equi, Anaplasma equi) is a tick-borne disease characterized by fever, anorexia, depression, limb edema, jaundice, petechiation, reluctance to move,
and ataxia. While the disease is most common in California, outbreaks have been reported throughout the Northern and Southeastern
United States. Now that this disease is correctly recognized as A. phagocytophilum, clearly this is one of the most common causes of infectious anemia and thrombocytopenia in domestic animals. This disease
is currently considered the most common tick-borne disease of animals in Europe. However there are many "genotypes" of this
organism which may result in some phenotypic presentations that differ in hosts and geographically so that disease is identified
in one species in a particular locale more often than another. Occurrence of disease may also be dependent on tick species
which harbor the bacterium. Nonetheless, emergence of this disease can occur in a particular mammalian species or tick given
the dynamic variation in gene expression of this organism. This organism has a very broad host range and actually sheep are
a very important reservoir. In addition mice and deer are also reservoirs which maintain this organism within the environment.