An investigation into the clinical pathological changes and serological response in horses experimentally infected with Babesia equi and Babesia caballi.

The study investigates the clinical and pathological changes in horses infected with two types of Babesia infections, and the associated serological response. The research found moderate symptoms in infected horses, along with changes in blood factors and serum concentrations, while also providing insight into the timeline of antibody detection post-infection.

Study Methodology and Disease Progression

• The researchers began with serologically negative horses, meaning these horses had no discernible antibodies for the Babesia infections as per an indirect fluorescent antibody test (IFA).
• These horses were sequentially infected, first with Babesia equi and then, 60 days later, with Babesia caballi.
• The most noticeable clinical signs observed in these horses were fever and slight jaundice (icterus), indicating an ongoing infection.

Impact on Blood and Serum Variables

• Haematological changes were noted in the horses’ blood. There was a decline in haematocrit and haemoglobin concentration, signifying a potential decrease in the oxygen-carrying capacity of the blood due to the infection.
• Platelet counts also dropped, which could impact the blood’s ability to clot effectively.
• The serum concentrations of albumin, iron and phosphorus diminished post infection. Reduced albumin could affect the body’s fluid balance and tissue nourishment, the drop in iron can inhibit red blood cell production, and less phosphorus can impact energy transfer and storage.
• An increase was noted in serum bilirubin and fibrinogen levels. A surge in bilirubin is often associated with liver disease or breakdown of red blood cells, while increased fibrinogen signifies an inflammatory response in the body.

Antibody Response and Parasitaemia

• Antibody titres against the Babesia infections were measured using the IFA and complement fixation (CF) tests.
• For B. equi infection, antibodies were detected between 10 to 19 days on the IFA and 12 to 38 days on the CF test.
• Comparatively, with B. caballi infection, antibodies were first noted between 6 to 8 days after infection on the IFA.
• The level of parasitaemia, which indicates the presence of parasites in the horse’s blood, remained below 1% for both B. equi and B. caballi infections, suggesting a relatively lower parasite load.