TheileriosisEast Coast Fever By Julie Murchie and Victoria Paesani
East Coast Fever • Phylum Apicomplexa • Caused by a tick-borne obligate intracellular parasite, Theileria parva, in sub- Saharan Africa, infecting ungulates • Major constraint to livestock production & food security in many developing countries • Causes high morbidity & mortality, killing 1 million cattle every year • Prevents introduction of very productive but disease-susceptible breeds of cattle • Expensive to control • Places a huge economic burden on poor smallholder farmers • Costs nearly $170 million yearly • Some African counties use the cattle as forms of currency • T. parva has ability to induce cancer in host cell in a way that is reversible • Studies have provided clear links to cancer biology in humans • Studying this parasite has given researchers clues for the right direction • Vaccines have the power to eradicate the disease • Not hazardous to human health Brown Ear Tick
Geographic Range • Threat mostly in eastern, central, & southern Africa
T. parva Primary Hosts Cattle * Waterbuck Indian Water Buffalo* African Buffalo • *develop symptomatic infections
5) …divides with schizont inside 2 infected daughter cells • 6) 10-15 days post-infection, schizont merozoite (invades erythrocyte (RBC)) • 4) Lymphocyte lymphoblast (enlarged lymphocyte) and… • * 5-8 days post-infection: found in lymph nodes • * Schizonts increase 10-fold every 3 days • 7) In RBC, merozoite piroplasm (infect ticks) • 3) Sporozoite enters lymphocyte (WBC) schizont • 2) Sporozoites transfer to ungulate if tick is attached for 48-72 hrs • 1) Sporozoites produced in tick salivary glands • 8) RBCs ingested by nymphs during feeding • 9) Once in gut, undergoes sexual reproduction motile stage, moves to tick’s salivary gland • Incubation Period • Experimentally Infected: 8-12 days • Naturally Infected: up to 3 weeks
Clinical Signs FirstSigns appear 7-25 days after tick attaches • Parotid gland swells • Ear is preferred feeding site • Fever • Anorexia & decrease in overall condition Later Signs • Lacrimation, corneal opacity • Nasal discharge, terminal dyspnea • Interlobular emphysema & sever pulmonary edema • Before death, temperature falls & dyspnea intensifies • Some develop neurologic disease “turning sickness” • Due to affected cells blocking circulation in capillaries within the CNS • Death (18-30 days after infestation by ticks) • The few survivors become lifelong immune carriers. Majority of these cases, asymptomatic carriers can be recognized with little or no effect ontheir productivity. Minority develop chronic disease problems that result in stunted growth in calves and lack of productivity in adult cattle.
Treatment, Prevention, & Control • Vaccination • Infect animal with the sporozoite form of the parasite while at the same time treating the cattle with an antibiotic drug to lessen the severity of the infection • Pasture Management • Herd-Selection of Resistant Animals • Tick Control & Eradication
Matovelo et al. 2003 Induction of Acquired Immunity in Pastoral Zebu Cattle Against East Coast Fever After Natural Infection by Early Diagnosis and Early Treatment Case Study
Objectives • 1. Examine efficiency of chemotherapy of natural ECF cases to look at protectiveimmunity against ECF in cattle. • 2. Design a regimen farmers can use to help minimize cattle loss due to ECF. This is done by establishing early disease diagnosis and early treatment.
Methods And Materials • Two villages in the Morogoro Rural District • Two seasons (April and November) • Ear tagged 280 calves
Methods And Materials • Farmers were trained to monitor the animals for clinical symptoms of ECF. • Qualifying clinical symptoms: enlargement of superficial lymph nodes, increase inbody temperature, dullness, and respiratory distress. • Animals diagnosed with ECFwere treated with buparvaquone. • Severity of the disease at the time of treatment was categorized based on the criteria set for ECF clinical reactions with some modifications.
Methods And Materials • Treatment responses were categorized as prompt/rapid, slow, or died. • Examined serum antibodies to T. parva, with samples at the beginning and end of study, using ELISA. • Studied blood and lymph node smears forT. Parva parasites.
Results • 100 animals were diagnosed with ECF • Most prominent clinical signs were fever and lymph node enlargements. • 81% of animals were positive for ECF on at least one screening method. • During follow-up, only 5 individuals were diagnosed with ECF a second time.
Discussion • Majority of cattle that were treated recovered. (98% recovery rate) • Shows that early diagnosis and early treatment is a reliable means to diagnose cattle with ECF on a basis of clinical signs in endemic areas. • Reliable early signs of infection are fever and swollen lymph nodes.
Discussion cont. • Use of chemotherapy with the early detection and early treatment approach reduced mortality and helped cattle develop immunity. • In terms of immunization, the early detection and early treatment approach is a reasonable alternative to the infection and treatment.
Conclusion • East Coast Fever is caused by Theileria parva • Hosts • Intermediate= cattle • Definitive= ticks • Incubation time is anywhere from 8 days to 3 weeks. • Very expensive • High morbidity & mortality rates • No harm to human health
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