EQUINE | Disease
EQUINE | Disease
to 50 %, while most animals in endemic areas survive infection . There is no documented cross protection between T . equi or B . caballi and horses can be infected with both parasites simultaneously .
Concurrent infectious diseases , plant poisonings and immunosuppressive conditions ( including immunosuppressive therapy ) can result in clinical babesiosis in carrier animals , as a consequence of recrudescence of infection . Concurrent infections with African horse sickness have been well documented and horses presenting with signs of oedema of the head ( supraorbital fossae ), limbs and ventral abdomen , in conjunction with anemia and icterus should be assessed for concurrent African horse sickness infection .
• Peracute : rare form of the disease usually only documented in naïve animals , with the only clinical observation being animals found moribund or dead .
• Acute : this is the most common form of clinical piroplasmosis characterized by fever ( greater than 40 ° C ), reduced appetite and malaise , elevated respiratory and pulse rates , congested mucous membranes , petechial hemorrhages , hematuria and fecal balls that are smaller and drier than normal . These impactions are sometimes followed by diarrhea . Disseminated intravascular coagulation has been reported in some cases .
• Subacute : anemia , icterus , and thriftiness together with weight loss and intermittent fever .
• Chronic : mild inappetence , poor performance and drop in body mass .
• Atypical forms : pneumonia , pulmonary edema , cardiac arrhythmia , catarrhal enteritis , laminitis and neurological disease .
• In-utero : infection of pregnant mares with Theileria equi at any stage in pregnancy is quite common . The consequence of infection depends on the stage of infection but includes reproduction failure ( involved in up to 11 % of all failures in South Africa ), abortion , neonatal piroplasmosis ( 2 to 3 days of age ) and birth of asymptomatic carriers . Infection with Theileria equi can be persistent with development of carrier mares which can produce further infected fetuses , randomly in subsequent pregnancies .
Clinical Pathology .
Low platelet and red blood cell counts in conjunction with reduction of hemoglobin concentration in conjunction with neutropaenia and lymphopaenia are typical hematological findings in clinical equine piroplasmosis . Decreased plasma fibrinogen , elevated bilirubin , low serum phosphorus and iron plus hemoglobinuria have also been documented .
Gross Pathology
In adult animals dying of acute disease pathology observed is largely a consequence of intravascular hemolysis . Mucous membranes are pale and / or icteric and blood may appear thin and watery . There is frequently hepatomegaly with orange brown discoloration , marked splenomegaly while kidneys are either pale and flabby ( hypoxic renal tubular necrosis ) or dark red / black ( hemoglobinuric nephrosis ). Subepicardial and subendocardial hemorrhages are also frequently documented , accompanied by hydropericardium and hydrothorax . Parasites are normally demonstrated in histological sections with Giemsa stains ( figure 3 and figure 4 ). Aborted fetuses / neonatal foals usually demonstrate anaemia , moderate to marked icterus , petechiae on visceral and serosal surfaces , hydrothorax , splenomegaly and hepatomegaly ( figure 5 and figure 6 ). Parasitaemia in spleen , blood and tissue
10 • Equine Health Update •