DISEASE RISK MANAGEMENT: THEILERIA FACTS – BLOG PART 2

Refer to Part 1 of this blog here.

Symptoms of Theileria T. Parva

Clinical signs of Theileriosis include, but are not limited to, fever and enlarged lymph nodes near the location of the tick bite(s). Other symptoms which may indicate the presence of these parasites include anorexia, dyspnoea, corneal opacity, nasal discharge, frothy nasal discharge, diarrhoea, pulmonary oedema, leukopenia, and anaemia.

The first clinical sign of Theileriosis is usually a swelling of the draining lymph node, usually the parotid, as the ear is the preferred feeding site of the vector; this is followed by a generalised lymphadenopathy in which superficial lymph nodes such as the parotid, prescapular, and prefemoral lymph nodes can easily be seen and palpated they may become greatly enlarged and present as hyperplastic, haemorrhagic, and oedematous. In acute cases, lymph nodes are oedematous and hyperaemic, but often become necrotic and shrunken in more chronic disease.

Fever ensues and continues throughout the course of infection; this rise in temperature is rapid and may reach up to 42°C. There is marked petechial and ecchymotic haemorrhage on most mucous membranes of the conjunctiva and the buccal cavity. Anorexia develops, and loss of condition follows.

Other clinical signs may include lacrimation, corneal opacity, nasal discharge, terminal dyspnoea, and diarrhoea, emaciation, dehydration and lesions. A frothy exudate is frequently seen around the nostrils of an ECF-infected animal

At the time of severe clinical disease or death, anaemia, jaundice, enlarged lymph nodes, muscle wasting, pulmonary oedema, and haemorrhagic enterocolitis may all be present. Before death the animal is usually recumbent, the temperature falls, and there is a severe dyspnoea due to pulmonary oedema that is frequently seen as a frothy nasal discharge.

The severity and time course of the disease depends on, among other factors, the magnitude of the infected tick (Theileriosis is a dose-dependent disease), and on the strain of parasites.

Death will usually occur 15–25 days after infection.

Diagnosis of Theileria T. Parva

Diagnosis of acute theileriosis is based on clinical signs, knowledge of disease, and vector distribution as well as examination of Giemsa-stained blood, lymph node and tissue impression smears. Theileriosis parva is diagnosed by the detection of schizonts in white blood cells or piroplasms in erythrocytes. The piroplasmic stage follows the schizont stage and it is usually less pathogenic and thus often found in recovering or less acute cases. It is hoped that a combination of enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR) and DNA probes will greatly enhance our present capacity to identify infected animals, thus making possible eradication of all Theileria species.

Treatment of Theileria T. Parva

The only beneficial drug which is effective in killing Theilerial schizonts and piroplasms, without sterilizing the infection is Parvaquone or buparvaquone. This drug is not registered in RSA, due to the eradication policy of the country regarding East Coast fever and Corridor disease (T.parva) in domestic cattle. A special permit is needed to acquire this drug, and even then, only about 50% of cases can be saved (if treated soon enough)) under veld conditions. The one major obstacle in game therapeutics is the need to most often than not immobilize animals to administer treatment (as doses are too big for drop-out darts). These immobilizing drugs compromise the clinical state even further and together with the stress induced when darting an animal, the chance of recovery is greatly hampered.

Supportive treatments include:

Intravenous therapy with colloids, and crystalloids may help with treating Theileriosis.
Blood Transfusions, where the source of the blood should preferably be from the same species of animal; however success has been achieved by using goat blood. Cortisone treatment should always be part of the treatment program as its beneficial effects outweigh its detrimental effects in this disease. A low dose of Heparin can also be given.

Unfortunately, it’s very seldom that any supportive treatment without buparvaquone or parvaquone will successfully treat this condition. All it might help with is to extend the disease process far enough to the point where the animal’s own immune system, can combat the disease.

Control of Theileria T. Parva

Control measures at Purple Rain Game Breeding include:

The rotation of animals between camps, to ensure that certain breeding camps remain empty, and are left to stand for the entire life cycle of the Rhipicephalus appendiculatus (Brown Ear) tick. Thus avoiding the transmission of the parasite from vector to animal.
Careful inspection and monitoring of animals for ticks, clinical symptoms of Theileria T. Parva and daily monitoring of the parasite count in faecal matter.
Maintaining a careful balance between inoculation and allowing the animals to build up their own immune system to defend themselves against these types of diseases.

Sources *http://www.oie.int/fileadmin/Home/fr/Health_standards/tahm/2.04.16_THEILIERIOSIS.pdf *http://www.oie.int/fileadmin/Home/eng/Animal_Health_in_the_World/docs/pdf/Disease_cards/THEILERIOSIS.pdf *http://www.afrivip.org/sites/default/files/theileria_4_control.pdf *https://en.wikipedia.org/wiki/East_Coast_fever *http://www.merckvetmanual.com/mvm/circulatory_system/blood_parasites/theileriases.html *A review of Theileria diagnostics and epidemiology Ben J. Mans a,b,c,*, Ronel Pienaar a, Abdalla A. Latif a,b *SAVA WILD LIFE GROUP: Theileriosis in Roan antelope