Congenital Toxoplasmosis in Humans and Domestic Animals

Toxoplasma gondii is an obligate intracellular parasite, and its infectious stages are: sporozoites, tachyzoites and bradyzoites in tissue cysts. The life cycle of T. gondii is a heteroxenous system that alternates between sexual and asexual stages. Ingestion of raw or undercooked meat with cysts, sporulated oocysts and congenital infections is the principal route of infection. T. gondii usually parasitizes the host without producing clinical signs. However, the infection leads to several neurological and ocular problems, and lead immunosuppressed individuals to severe clinical conditions. For livestock animals, the infection leads to abortion and neonate mortality. The prevalence of antibodies is reported worldwide in humans and animals. Toxoplasmosis is considered one of the most important parasitic infections of human. For diagnosis and epidemiologic studies, several methods are used, for instance: serology to detect antibodies anti-T.gondii, parasite isolation in laboratory animals (bioassays) or protozoan observation through direct molecular methods to detect the DNA of T. gondii. Recent studies on T. gondii virulence and genotyping using standard methods revealed different results in South America, Africa and Asia. These results were different from those observed in North America and Europe.

Notwithstanding, the severity of the sequels and the frequency of occurrence, congenital toxoplasmosis in humans continues to be a neglected disease in several countries, including Brazil. This is partly because a large proportion of infected children are asymptomatic at birth, and consequently are not diagnosed and treated during the first year of life, while most develop ocular and neuro–psycho–motor sequels in early adulthood. The disparity of several management protocols for acute toxoplasmosis has resulted in extreme difficulty for the physicians to make decisions, resulting in many patients being subjected to unnecessary therapies and invasive procedures or are not treated adequately. Another great difficulty lies with the diagnosis, since most pregnant women are asymptomatic when infected, while diagnosis is based on laboratory results, whose interpretation is dependent on several factors, including screening and confirmatory tests and the gestational age when blood sample was taken. Another difficulty is related with the post–natal diagnosis, because in many neonates, it is not possible to detect specific IgM antibodies, and the presence of IgG does not confirm an infection, since these can be passively transferred from the mother to the infant. Faced with this dilemma and based on the work of our group with patients, communities, health services, this team of specialists have accumulated widespread knowledge for the elaboration and implementation of the “Health surveillance program of gestational and congenital toxoplasmosis in Londrina, Paraná, Southern Brazil”. This successful program has served as the basis for this chapter.

Toxoplasma gondii is an apicomplexan protozoan parasite that infects a broad range of hosts, including dogs. Due to the high rate of dogs naturally infected with T. gondii and its correlation with immunosuppressive diseases, attention should be paid to the occurrence of this parasite in canine population, especially puppies, which are considered of high risk for developing the disease. Toxoplasmosis in puppies is particularly important, because the effects of the disease may have consequences on animals’ lives, and they may have immeasurable value, being considered as family members. The main objective of this chapter will be to discuss important aspects involving congenital toxoplasmosis in this animal species.

Toxoplasma gondii is a protozoan which commonly infects cats, dogs and humans, causing toxoplasmosis. This disease, of great importance in public health, is acquired by consumption of meat and by-products containing cysts, ingestion of food and/or water contaminated with oocysts, as well as through the placenta. Congenital Toxoplasma infections are reported in many species, being relevant in both medicine and veterinary medicine. In cats, congenital toxoplasmosis is associated with the occurrence of injuries in the liver, lungs, central nervous system and eyes, observed when hosts are infected in the middle to the last thirds of pregnancy. Ocular form can occur in young cats, infected through placenta, with no other clinical signs. The objective of this chapter is to describe the main manifestations of congenital toxoplasmosis in cats.

T. gondii is prevalent in most areas of the world and is of veterinary and medical importance, because it may cause abortion or congenital disease in its intermediate hosts. In sheep, T. gondii is an important cause of abortion, which can result in considerable economic losses. Herbivores acquire infection mainly by the ingestion of oocysts in water or contaminated food. Seroprevalence of T. gondii in sheep have been reported extensively in different countries and the positive rates ranged from 3% to 95%. The diagnosis of toxoplasmosis can be made by means of indirect methods such as serological evaluation to detect specific antibodies. The hypothesis that primary infection protects against reinfection is the basis for many farmers not to discard sheep with a history of abortion. However, recent studies have suggested that sheep persistently infected with T. gondii may transmit the infection congenitally more frequently than expected. Ewes persistently infected with c transmitted the infection congenitally, possibly due to an acute relapse process. This result shows that the immunity acquired in the primary infection did not protect the ewes against future T. gondii reinfections. The experimental T. gondii reinfection triggered severe reproductive alterations (locomotive changes, malformations, stillbirths and disability) in Santa Inês ewes primarily infected at different pregnancy stages. Therefore, congenital T. gondii infection was common when ewes were chronically infected prior to pregnancy, with or without reinfection during at various stages of gestation.

Toxoplasma gondii is a protozoan parasite distributed worldwide. It is an obligatory intracellular parasite which can infect a wide variety of vertebrates and different host cells. Usually, T. gondii infect pigs without causing any clinical signs. However, although rare, it may provoke disease, presenting fever, anorexia, depression and abortion. Pork is considered the main infection source for humans, and the risk of acquiring infection through the consumption of raw or undercooked meat, which is common in many regions, shows that the control of swine toxoplasmosis plays an important role in the epidemiology of the disease. This chapter discusses aspects related to the parasite-host relationship between T. gondii and pigs, such as epidemiology, natural (congenital) and experimental infections, diagnosis, vaccines and prevention.

Toxoplasmosis is a public health issue and an obstacle to the breeding of goats. This zoonosis results in great economic losses in human beings and production animals, being both infected from the food and water intake contaminated with Toxoplasma gondii oocysts and this parasite causes severe clinical consequences, among them reproductive problems. In caprines, the presence of antibodies against T. gondii is common in herds. For this reason, toxoplasmic reinfection in these animals can not be ruled out or neglected in animals naturally infected with T. gondii. In this way, the objective of this chapter is to describe the main aspects of congenital toxoplasmosis in pregnant goats, in different gestational stages, infected and reinfected with T. gondii and their offspring.

Toxoplasma gondii is a parasite of the phylum Apicomplexa. It is an obligate intracellular protozoan that affects humans and a diverse range of vertebrate hosts. The infection of herbivores occurs primarily through ingestion of oocysts in food and contaminated soils and water. Natural infection by T. gondii in cattle was originally reported in Ohio, USA, which also reported the first experimental infection by this protozoan in cattle. The congenital transmission of T. gondii in cattle was originally described in 1980. The congenital transmission may frequently be affected by the pathogenicity of the T. gondii strain and this zoonotic parasite is example of endogenous and exogenous transplacental infection, which emphasizes the need for greater precision in describing field or experimental research that describes infection passing from cows to fetuses, as well as the actual importance of cattle, in different countries, on the epidemiology of toxoplasmosis.