Control options forNeospora caninum– is there anything new or are we going backwards?

Abstract

Recent work has highlighted and enumerated the economic annual losses due to Neospora caninum abortions worldwide, which should provide strong motivation for the control of bovine neosporosis. However, with the recent withdrawal from sale of the only commercially available vaccine, control options for N. caninum have become more restricted. While researchers continue to work on developing alternative efficacious vaccines, what are the control options presently available for the cattle industries? At the practical level, recommendations for 'Test-and-cull', or 'not breeding from seropositive dams' stand diametrically opposed to alternative options put forward that suggest a primary producer is better advised to keep those cows in the herd that are already seropositive, i.e., assumed to be chronically infected, and indeed those that have already aborted once. Treatment with a coccidiostat has been recommended as the only economically viable option, yet no such treatment has gained official, regulatory approval. Dogs are central to the life cycle of N. caninum and have repeatedly been associated with infection and abortions in cattle by epidemiological studies. Knowledge and understanding of that pivotal role should be able to be put to use in control programmes. The present review canvasses the relevant literature for evidence for control options for N. caninum (some of them proven, many not) and assesses them in the light of the authors' knowledge and experience with control of N. caninum.

Neospora caninum is the leading cause of bovine fetal loss in British Columbia, Canada

“…Here, the parasite expands asexually to produce a chronic infection harboring infectious cysts that are transmissible to canids. In cattle, it is also efficiently transmitted vertically by transplacental infection, with congenital transmission rates recorded to be 40–95% among calves born to seropositive mothers (Reichel et al 2014). …”

The effect of a live Neospora caninum tachyzoite vaccine in naturally infected pregnant dairy cows

“…It has been considered that an effective vaccine against neosporosis should either be aimed to prevent infection in uninfected animals, or to prevent abortion or vertical transmission in infected animals (Innes et al, 2002). Previous studies demonstrated that vaccination of naïve cows with live tachyzoites was protective against experimental challenge (Williams et al, 2007;Rojo-Montejo et al, 2013;Weber et al, 2013;Hecker et al, 2013;Reichel et al, 2014;Monney and Hemphill, 2014). The Israeli N. caninum NcIs491 isolate, obtained from brain tissue of an aborted fetus, can be easily grown in culture and is suggested to be of low pathogenicity to laboratory animals including gerbils (Fish et al, 2007) and mice (unpublished results), in comparison with the NC-1 strain (Lindsay et al, 1995;Rettigner et al, 2004).…”

Prevalence and distribution of Neospora caninum in water buffalo ( Bubalus bubalis ) and cattle in the Northern Territory of Australia

“…Tachyzoites are transmitted transplacentally to the foetus during pregnancy and may cause abortion. Currently, no economically viable method of controlling the disease has been established [4].…”