A research team has developed a laboratory test it says will be suitable for large-scale testing of drugs against the protozoa that cause troubling infections in cattle and horses, including equine piroplasmosis.
Drug therapies against these tick-borne infections remain extremely limited, with infected US horses escaping euthanasia only if they are enrolled in a research program supervised by the US Department of Agriculture.
The group of infections, known as babesiosis, are known to bring great economic losses in the bovine and equine industries around the globe.
Babesiosis in cattle is caused by Babesia bovis and Babesia bigemina, with a considerable impact on cattle health and productivity.
Equine piroplasmosis, caused by Theileria equi and Babesia caballi, is considered one of the most important protozoan diseases affecting horses, mules, and donkeys.
The research team said that a rapid and accurate laboratory test was required for evaluating antibabesial drugs on a large scale, citing what they described as an urgent need to develop more effective and safer treatments.
They reported in the open access journal, PLOS ONE, that they had identified a fluorescence-based test that could be used for determining the effectiveness of antibabesial compounds.
Their test did not require daily replacement of a culture medium, making it highly suitable for laboratory-based large-scale drug screening against Babesia and Theileria parasites.
It relied on the high throughput screening of red blood cells to detect parasite DNA using a fluorescent spectrophotometer.
They described the test as providing accurate, simple, and rapid detection of the parasites in question.
Babesiosis infections can result in fever, anemia and sometimes death.
Chemotherapy by imidocarb dipropionate and diminazene aceturate is currently the most common strategy for controlling infection in the field, but there are concerns about toxicity. Resistance to these drugs has also emerged.
Mohamed Abdo Rizk and his colleagues said developing safer antibabesial treatments was worthy of priority in veterinary research.
The researchers said that the quest for future drugs to combat the infections should be shifted to the laboratory screening of large-scale chemicals either commercially available or non-commercially available. Those showing promise could then be assessed in the field.
They noted in their work that luteolin and pyronaridine tetraphosphate drugs exhibited the best growth inhibition of bovine and equine protozoa next to diminazene aceturate, followed by nimbolide, gedunin and enoxacin.
“These drugs might be more effective if used as part of a combination therapy rather than a single therapy,” they suggested.
Further studies were required, they said.
Rizk MA, El-Sayed SAE-S, Terkawi MA, Youssef MA, El Said ESES, et al. (2015) Optimization of a Fluorescence-Based Assay for Large-Scale Drug Screening against Babesia and Theileria Parasites. PLoS ONE 10(4): e0125276. doi:10.1371/journal.pone.0125276
The full study can be read here.