Longitudinal study of an outbreak of Trypanosoma evansi infection in equids and dromedary camels in Israel.

The research discusses a longitudinal study of an outbreak of Trypanosoma evansi infection affecting horses, camels, and donkeys on a farm in Israel. This was the first reported outbreak of its kind in domestic animals within the country. The infection was most prevalent in camels and showed severe anemia in symptomatic animals.

Introduction and Context

• The outbreak in question was caused by Trypanosoma evansi, a neurally invasive parasite responsible for serious disease in various domestic and wild animals.
• It was the first recorded outbreak of T. evansi in domestic animals in Israel and included horses, camels, and donkeys.
• The main concern for veterinarians and farmers was the infection rate, with 80% of camels, 43% of horses, and 46% of donkeys being affected.

Methodology

• The research team undertook a longitudinal study of the outbreak, observing it over two distinct phases.
• Various methods were used for the detection of the infection, including clinical monitoring, blood smears, packed cell volume (PCV), serology, and polymerase chain reaction (PCR), a technique used to amplify trace amounts of DNA, followed by reverse dot blot (RDB) for molecular detection of the infection.

Findings

• Clinical disease, as indicated by characteristic symptoms, anemia, and parasitemia, was evident in four camels and one horse.
• Six other animals were identified as asymptomatic latent carriers by a positive RDB, and an additional six animals were considered suspected carriers due to being seropositive – displaying a positive result in a test of blood serum.
• On average, animals showing symptoms had significantly lower PCV, indicating more severe anemia as compared to latent carriers that showed no outward signs of infection.

Treatment and Complications

• Two camels that were diagnosed with severe trypanosome parasitemia exhibited an anaphylactic-like reaction – a severe, potentially life-threatening allergic reaction – immediately after treatment with melarsenoxide cysteamine, a medication used to treat trypanosomiasis. This reaction proved fatal in one of the cases.
• A recurrence of the infection was observed in one camel four months after treatment showed the persistent nature of the parasite and the challenges in controlling the infection.