Diagnosis and Treatment of Eperythrozoonosis in Foxes
Fox eperythrozoonosis is an infectious disease caused by Eperythrozoon attaching to the surface of fox red blood cells and floating free in the plasma. In July 2003, a disease with symptoms of elevated body temperature, difficulty breathing, and blood flowing from the nose was found in foxes at a breeding park in a certain city. Through on-site clinical symptom observation, pathological necropsy, and laboratory diagnosis, it was confirmed as fox eperythrozoonosis. The diagnosis and treatment situation is introduced as follows.
1 Incidence situation
Among the fox breeding specialized households in the breeding park of a certain city, there were 2 households. On July 2, 2003, 8 foxes became ill, on July 9 another household had 5 foxes become ill, and by July 15 the 2 households had a total of 21 foxes become ill, among which 17 were cub foxes. During the onset period, 8 died, among which 7 were cub foxes, with a mortality rate of 41.2%, and an adult fox mortality rate of 25%.
2 Clinical symptoms
2.1 Acute type
On the evening 1 day before onset, appetite, drinking, and activity were all normal, and on the second morning they died in the cage; some foxes suddenly fell to the ground after eating, convulsed, foamed at the mouth, and died rapidly.
2.2 Subacute type
Body temperature rose to 41-42°C, difficulty breathing, foamy blood flowing from the nose, intermittent convulsions throughout the body, and then death, with a disease course of 1-2 days.
2.3 Chronic type
Mostly in the later stage of disease, intermittent convulsions, death after lasting 5-8 days.
3 Necropsy lesions
Blood vessel hemorrhage and congestion in the brain, with pinhead-sized hemorrhage points in the brain parenchyma. Large-area congestion and hemorrhage in the lungs, appearing purple-black. The pericardial sac accumulated pale yellow or pale red fluid, the color became lighter, and there was strip-shaped hemorrhage in the endocardium. The liver was enlarged, earth-yellow in color, with unclear cut surface, and the gallbladder was full. The stomach was pale, with filamentous hemorrhage on the surface. Hemorrhage in the bladder mucosa, diaphragm, and peritoneum.
4 Laboratory diagnosis
4.1 Blood compression smear
Collect blood from the forearm vein of a diseased fox and drop it on a slide, add an equal amount of physiological saline, mix evenly, cover with a cover glass, and observe under a microscope. Small bodies (Eperythrozoon) of spherical, oval, bean-like, and granular shapes can be seen attached to the surface of red blood cells, constantly moving, twisting, and turning. With the movement of Eperythrozoon, the morphology of red blood cells also becomes deformed, showing up-and-down tremor or left-right swinging, causing red blood cells to take different shapes such as gear-like, cone-shaped, triangular, quadrilateral, and oval.
4.2 Blood smear
Take a venous blood smear, perform Wright's staining and microscopic examination, and many purple-blue, highly refractive Eperythrozoon of various forms such as round, oval, and short rod-shaped can be seen on the surface or edges of red blood cells.
Based on clinical symptoms, necropsy lesions, and laboratory diagnosis, it was confirmed as fox eperythrozoonosis.
5 Prevention and treatment
① Intramuscular injection of Hematochinol (Berenil), diluted with water for injection or physiological saline into a 5% solution, at 3-5 mg/kg body weight, deep intramuscular injection, once every 48 hours, for 3 consecutive injections. ② Injection of Xuechongqing at 0.2-0.3 mL/kg body weight, intravenous or intramuscular injection, once every 24 hours, for 3 consecutive injections. ③ Injection of Xuechongsha at 0.2-0.3 mL/kg body weight, intravenous or intramuscular injection, once every 48 hours, for 3 consecutive injections. ④ Antibiotics tetracycline and oxytetracycline at 10 mg/kg body weight and chlortetracycline at 15 mg/kg body weight orally, or intramuscular injection, or intravenous injection, for 7-10 consecutive days. Using the above therapies, the effect was good.
6 Summary and discussion
① The household owners mistakenly regarded it as a common fox disease in the early stage of onset, and treatment was ineffective; therefore, once a suspicious fox group is found, fresh blood Eperythrozoon examination should be carried out early, confirmed in time, and measures taken promptly to eliminate the source of infection. ② Fox Eperythrozoon mostly uses arthropods as transmission vectors; therefore, the pathogen transmission route must be thoroughly eliminated, and blood-sucking insects such as mosquitoes, flies, sarcoptic mites, and lice should be regularly expelled and killed, and environmental disinfection should be done well to reduce morbidity and mortality. ③ For severely diseased foxes, antibiotic drugs can also be used for symptomatic treatment to prevent secondary infection. ④ After using Xuechongqing and Xuechongsha injections for 3-4 hours, the drugs kill part of the parasites, which will cause the fox's body temperature to rise; under general circumstances, there is no need to use drugs to lower the temperature.