Pig producers on guard after discovery of drug-resistant coccidiosis
Microbiologists are warning European pig producers to monitor the success of coccidiosis treatment toltrazuril after discovering the first signs of resistance to the drug.
Scientists at the University of Veterinary Medicine, Vienna, identified a strain of coccidiosis-causing cytoisospora suis that is not affected by toltrazuril — the standard treatment for the diarrhea-causing intestinal parasite.
In a study published in the journal Parasites & Vectors, they said farmers should monitor resistance by checking for parasite eggs — known as oocysts — in fecal matter.
They also said farmers should increase their hygiene measures to prevent infections which, though rarely fatal, can spread rapidly and significantly hamper piglet growth, leading to economic losses.
Signs of the resistant strain or isolate of the parasite were first identified on a Dutch pig farm in 2014, when the farmer reported an increase in diarrhea in newborn pigs that had been treated with toltrazuril.
Until that point, there had been no signs of resistance to the drug, which European producers have used as a standard treatment for about 20 years.
In a subsequent trial carried out by scientists, piglets infected with the isolate from the Dutch farm developed diarrhea by the fourth day of infection, even though they had been given a minimum dose of 20mg/kg body weight of medication.
Signs of oocysts — which are only found when the drug takes no effect — were also detected in all fecal samples.
Head researcher Anja Joachim said that resistance to toltrazural is developing slowly, but is expected to become more frequent.
As there are no practical alternatives to controlling the parasite, she said it is vital farmers carry out frequent monitoring, as well as increasing hygiene measures to prevent any spread of pathogens.
“These routine checks can be performed easily,” Joachim said. “When oocysts are discovered in the feces despite the administration of toltrazuril, additional measures should be taken immediately.”
Improved hygiene measures and chemical disinfection in particular can keep down the number of oocysts in the environment of the piglets, she added.
“This is an essential prerequisite for preventing resistant parasites from spreading.
“As a consequence, it will be essential to consistently monitor the success of treatment in order to detect any developing resistance of the parasite.”