Detection of Oocyst‐Associated Toxoplasmosis in Swine from Southern Chile

Abstract

Pork has been traditionally considered an important source of human Toxoplasma gondii infection. Pigs, as other meat-producing animals, can become infected by the ingestion of oocysts that are shed in the environment by infected cats or by the consumption of cysts present in tissues of infected mammals, commonly small rodents. The objective of this study was to investigate the level of T. gondii infection in swine from southern Chile that can be associated with the ingestion of oocysts and therefore exposure to a contaminated environment. A total of 340 serum samples from swine were obtained from three commercial slaughterhouses located in the Araucania and Los Rios Regions from southern Chile. Study animals originated from local farms, mainly small commercial producers, and the meat is sold locally. Overall, 8.8% (30/340) of the samples showed T. gondii-specific IgG antibodies. Of these sero-positive animals, 80% (24/30) were also positive for antibodies specific against the oocyst stage of the parasite, indicating that animals had been infected recently by the ingestion of oocysts. The observed results suggest a high level of environmental contamination with oocysts on the farms of origin. In addition to the food safety problems associated with the consumption of meat from infected animals, the high level of environmental contamination on the farm represents a direct health risk for people living and/or working on these farms. Consequently, there is a need to develop on-farm monitoring programmes and identify risk reduction strategies (food storage, water purification, rodent control and contact with cats) that are appropriate and cost-effective for informal and outdoor type of farms.

CCp5A Protein from Toxoplasma gondii as a Serological Marker of Oocyst-driven Infections in Humans and Domestic Animals

“…In addition, our data showed 100% of positivity to CCp5A and STAg in samples from pigs raised extensively, resulting in naturally infected animals and indicating that the causative agent was the oocyst and suggesting a high level of environmental contamination by oocysts on the farm, where they had been raised. Similar results were observed using the TgERP protein in pig samples from slaughterhouses in Chile (80% of positivity; Munoz-Zanzi et al, 2012 ). These observations show the impact of the environmental contamination by oocysts in infected animals, which are used as food resources for humans, making clear that the identification of the infective form responsible for the infection is important.…”

“…The lack of this information hampers the accomplishment of procedures to prevent and control T. gondii infection, as the evidences of infection via oocyst is exclusively based on epidemiological surveillance studies, which can be inaccurate in many situations. These facts have also restricted the implementation of educational programs to reduce or minimize the risk factors associated with toxoplasmosis ( Hill et al, 2011 ; Munoz-Zanzi et al, 2012 ).…”

Agricultural landscape and spatial distribution of Toxoplasma gondii in rural environment: an agent-based model

“…Human infections result from the ingestion of parasite bradyzoites contained in contaminated meat, ingestion of oocysts from environmental sources, or congenital transmission [ 11 ]. Oocysts contribute to a large amount of infections in human and farm animals [ 15 , 16 ]. It is thus necessary to understand their spatial distribution in the environment in order to evaluate the risk of infection from the environment.…”

The Life Cycle of Toxoplasma gondii in the Natural Environment

“…The second useful tool that should bring relevant information is the development of methods to detect antibodies specifically linked to infection by oocysts [190]. This test, based on western blot assay detecting for IgG positive serums antibodies to sporozoites, allowed the authors to determine the proportion of cases that had contacts with oocysts in Chile, both in humans [191] and in swine [192]. In North America, a survey using this method shows that a high proportion of mothers of congenitally infected infants had primary infection with oocysts [193].…”