Efficacy of Toltrazuril 5 % Suspension against Eimeria bovis and Eimeria zuernii in Calves and Observations on the Associated Immunopathology

Abstract

16 Calves were each infected with suspensions containing a mixture of approximately 230,000 Eimeria bovis and 70,000 E. zuernii oocysts, which resulted in detection of oocysts in faeces of 12 of 16 calves by day +14 after infection. On day +14 after infection calves were either treated (n = 8) with toltrazuril at 15 mg/kg body weight or with a placebo. Observations were made on the clinical condition, faecal score and liveweight of calves daily from one day post infection (pi) until 24 days pi when all calves were euthanised and examined post mortem. Samples were collected from ileum and colon for histological, immunohistochemical and gene expression studies. The study demonstrated an efficacy of toltrazuril for the treatment of E. bovis and E. zuernii infections in calves reaching 99 % (based on arithmetic mean oocyst counts in faeces) within three days of treatment and remaining at or above this level for six days. Toltrazuril did not have a significant effect on the pattern and extent of immune cellular infiltration in the mucosa of ileum and colon, but the expression of the genes coding IL-2, IL-10 and TNF-α in the ileum and TNF-α in the colon were elevated in calves treated with toltrazuril. Higher levels of oocyst shedding were significantly associated with lower expression of genes coding for IL-2, IL-10 and higher IP-10. It is concluded that toltrazuril is effective for the treatment of coccidiosis due to E. bovis and E. zuernii in calves and enables the development of a normal or enhanced immune response to infection.

Bovine Eimeria species in Austria

“…The efficacy of toltrazuril against infections with Eimeria spp. was shown in various studies (Bohrmann 1991;Mundt et al 2003Mundt et al , 2005Epe et al 2005;Jonsson et al 2011). The additional costs for treatment are justified for all farms with a diagnosed problem of coccidiosis and for farmers who are focused on raising profitable and healthy dairy calves for progeny.…”

Prevalence of Eimeria spp. in calves from dairy farms in northern Paraná state, Brazil

“…In dairy herds in Holland, 46% of young calves and 43% of older calves presented infection by Eimeria spp., whereas only 16% of cows in the same herds were infected (CORNELISSEN et al 1995). This suggests that younger animals have higher susceptibility to coccidia, given that clinical cases are almost exclusively seen among animals in this age range (STOCKDALE, 1981;CHIBUNDA et al, 1997;JONSSON et al, 2011;BANGOURA et al, 2011).…”

“…During its life cycle, the parasite destroys the host's enterocytes, causing loss of blood, water, albumin and electrolytes to the intestinal lumen. These effects may lead to diarrhea, dehydration, prostration and eventually death, depending on the period of exposure and infective dose (JONSSON et al, 2011;ALMEIDA et al, 2011).…”

“…Among a fourteen known pathogenic species, E. bovis and E. zuernii are considered to be the most important, due to the severity of clinical cases caused in younger animals (JONSSON et al, 2011;BANGOURA et al, 2011;FLORIÃO et al, 2016). However, some authors have emphasized the importance of E. alabamensis as the causative agent of coccidiosis in animals feeding on pastures (SVENSSON et al, 1993(SVENSSON et al, , 1994MARSHALL et al, 1998;SVENSSON, 2000).…”

Comparative efficacy of diclazuril (Vecoxan®) and toltrazuril (Baycox bovis®) against natural infections of Eimeria bovis and Eimeria zuernii in French calves

“…Consequently, persistent or longer-acting treatments against coccidiosis in young calves could delay development of the immune response; and in this respect the toltrazuril-treated calves in this study displayed a peak of excretion prevalence 60 days after treatment, suggesting a detrimental effect on growth performance. It has previously been surmised that treatments with a benzene acetonitrile compound may have an effect on the development of immunity to coccidial infection in cattle and that if a treatment did interfere with the acquisition of immunity following subsequent reexposure, then severe disease may follow (Jonsson et al, 2011). A study conducted by Taylor et al (2011) with diclazuril given at 1 mg/kg BW (recommended dose) to lambs, demonstrated that at this dose level the treatment was effective in preventing coccidiosis in lambs, but at higher dose levels (2.0 and 4.0 mg/kg BW) it appeared to completely clear the lambs of coccidia rendering them susceptible to re-infection.…”