Toxoplasma gondii: from animals to humans

Summary: Throughout much of the world, Trichinella spp. are found to be the causative agents of human trichinellosis, a disease that not only is a public health hazard by affecting human patients but also represents an economic problem in porcine animal production and food safety. Due to the predominantly zoonotic importance of infection, the main efforts in many countries have focused on the control of Trichinella or the elimination of Trichinella from the food chain. The most important source of human infection worldwide is the domestic pig, but, e.g., in Europe, meats of horses and wild boars have played a significant role during outbreaks within the past 3 decades. Infection of humans occurs with the ingestion of Trichinella larvae that are encysted in muscle tissue of domestic or wild animal meat. Early clinical diagnosis of trichinellosis is rather difficult because pathognomonic signs or symptoms are lacking. Subsequent chronic forms of the disease are not easy to diagnose, irrespective of parameters including clinical findings, laboratory findings (nonspecific laboratory parameters such as eosinophilia, muscle enzymes, and serology), and epidemiological investigations. New regulations laying down rules for official controls for Trichinella in meat in order to improve food safety for consumers have recently been released in Europe. The evidence that the disease can be monitored and to some extent controlled with a rigorous reporting and testing system in place should be motivation to expand appropriate programs worldwide.

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Epidemiology, Diagnosis, Treatment, and Control of Trichinellosis

Monitoring of verotoxigenic Escherichia coli (VTEC) and identification of human pathogenic VTEC types 1 Scientific Opinion of the Panel on Biological Hazards

Control of the risk of human toxoplasmosis transmitted by meat

Toxoplasmosis in pigs--the last 20 years.

Serological surveys of the prevalence of antibodies against Toxoplasma gondii were carried out amongst swine and cattle in the Netherlands. Data were analysed according to the different categories of animals. The results show very low seroprevalences of Toxoplasma gondii in finishing pigs (1.8%) and in fattening calves (1.2%). In sows and dairy cattle, respectively, seroprevalences of 30.9% and 27.9% respectively, were found, demonstrating clearly the environmental infection pressure and illustrating the importance of housing and management in establishing low infection rates. Substantially different seroprevalences were found between dairy cattle sampled in the North and in the South of the Netherlands (13.1% and 42.6%, respectively). The infection rates in the samples from finishing pigs, fattening calves, and dairy cattle demonstrate that seroprevalences in individual farms or herds may differ considerably. Investigation of the factors involved can be useful in determining the causes of infection and for developing measures with regard to prevention. The very low seroprevalences in finishing pigs and fattening calves indicate, however, that the production of toxoplasma-free meat may be well within reach in modern husbandry. Since farm animals easily are infected, serological screening of individual farms or herds for the absence of T. gondii infection, as a part of the Integrated Quality Control programme, can be helpful in determining the quality of livestock production and in developing certain standards of hygiene for individual farms.

https://www.tandfonline.com/doi/pdf/10.1080/01652176.1995.9694539

Prevalence of antibodies to toxoplasma gondii in cattle and swine in the Netherlands: Towards an integrated control of livestock production

An enzyme-linked immunosorbent assay is described for the detection of serum antibodies to visceral larva migrans (Toxocariasis). Excretory-secretory antigens of the second-stage larvae ofToxocara canis were used as antigen to coat the polystyrene plates. With sera from patients high antibody titers were observed in both ocular and visceral disorders. Cross-reactions due to other parasitic infections could be excluded, including other migrating larval infections such as ascariasis, trichinellosis, strongyloidiasis, filariasis, and anisakiasis. In a small seroepidemiologic survey of healthy primary schoolchildren, a remarkably high percentage (7.1) reacted positively to this method. These children showed eosinophilia as compared to the seronegative group. The data were compared with those observed in other countries and the results prompt reconsideration of the significance ofT. canis for public health.

Visceral larva migrans: Examinations by means of enzyme-linked immunosorbent assay of human sera for antibodies to excretory-secretory antigens of the second-stage larvae ofToxocara canis

Sera from 58 cases of confirmed human trichinosis were examined over an 11-month period. The enzyme-linked immunosorbent assay (ELISA) was used for the detection of class-specific serum antibodies (IgG, IgM, IgA, IgE) and for total serum IgE. The indirect immunofluorescent test served as reference technique. The ELISA proved to be more sensitive. Specific IgG antibodies were detected by ELISA in 100% of the clinical cases. Both IgG and IgM were demonstrable throughout the observation period of 11 months. Specific serum IgA was seen in 62% of the patients during the first 3 months, presumably the result of stimulation of the immune system by the adult worms in the intestine. Specific serum IgE was seen in a few cases only at the onset of the disease. Total serum IgE levels were elevated in 32% of the patients in the first month of the disease and in 17% after 11 months, compared to 10% of healthy individuals.

Detection of specific immunoglobulins (IgG, IgM, IgA, IgE) and total IgE levels in human trichinosis by means of the enzyme-linked immunosorbent assay (ELISA).

A serological survey on toxoplasmosis was carried out amongst horses, sheep, cattle, pigs and poultry in the Netherlands. Sera were obtained from slaughter animals and the results were compared with those of previous studies of this kind in the Netherlands. In horses and cattle the percentage of seropositive animals remained the same in the past 20 years. In sheep and particularly in pigs, however, a remarkable decline of seropositive animals was found. This is probably due to the age of the animals examined and a change in present day methods of farming. In poultry it was shown that only free scratching hens were seropositive in up to 30 per cent of the animals tested, whereas broilers and battery animals were seronegative. Since as yet no individual control measures in the slaughterhouse exist with regard to toxoplasmosis it is recommended to carry out periodic epizootiological surveys amongst farm animals to be able to follow trends of the infection.

https://www.tandfonline.com/doi/pdf/10.1080/01652176.1982.9693848

J.H. Franchimont

Papers

Prevalence of antibodies to toxoplasma gondii in cattle and swine in the Netherlands: Towards an integrated control of livestock production

Visceral larva migrans: Examinations by means of enzyme-linked immunosorbent assay of human sera for antibodies to excretory-secretory antigens of the second-stage larvae ofToxocara canis

Detection of specific immunoglobulins (IgG, IgM, IgA, IgE) and total IgE levels in human trichinosis by means of the enzyme-linked immunosorbent assay (ELISA).

Prevalence of antibodies to toxoplasma in farm animals in the Netherlands and its implication for meat inspection.

Comparison of the enzyme-linked immunosorbent assay (ELISA) with three other methods for the detection of Trichinella spiralis infections in pigs