Detection of Theileria equi in spleen and blood of asymptomatic piroplasm carrier horses.

This research looked at whether horses without symptoms but infected with a parasite called Theileria equi store infected red blood cells in the spleen, and if having this parasite in the spleen is linked to parasitemia. The study found that some horses did have the parasite in their spleen without showing symptoms or having parasitemia, but showed infected red blood cells in the spleen.

Study Design and Samples

• The team took samples from 25 adult horses that showed no signs of illness. Both whole blood samples from the jugular vein and splenic puncture blood samples were collected from each horse.
• All samples were tested for blood cell counts and checked for the presence of Theileria or Babesia parasites.
• A procedure called PCR, which allows for the detection of specific DNA sequences, was used to identify any piroplasm infection, including T. equi and B. caballi.

Findings

• Of the 25 horses tested for piroplasm cells via PCR, seven (28%) were positive in their vein blood but negative in their splenic blood, five (20%) were positive in splenic blood but negative in jugular vein blood, and 13 horses (52%) tested positively in both vein and splenic blood samples.
• The research team also evaluated the horses’ hematological health and found that 13 out of 25 horses (52%) had anemia, five (20%) a reduction in lymph cells (lymphopenia), two (8%) showed elevated neutrophil levels (neutrophilia), and one each (4%) showed low neutrophil levels (neutropenia) and platelet deficiency (thrombocytopenia).

Implications

• This study discovered that a significant number of the symptom-less carrier horses tested – 20% – did not show parasitemia, but rather had infected red blood cells present in the spleen.
• The findings indicate that even in the absence of clinical symptoms or detectable parasitemia, horses can still harbor the T. equi parasite, potentially serving as reservoirs for the disease.
• The research provides valuable new insights that could potentially guide future diagnostic strategies to control the spread of T. equi infections amongst equine populations.