Experimental congenital infection of Toxoplasma gondii in Macaca arctoides

Congenital toxoplasmosis was studied in Macaca arctoides as a model for primates. Time-mated female monkeys were assigned to 5 experimental groups and inoculated with 4 different strains of Toxoplasma gondii before pregnancy and during various stages of gestation. All monkeys showed a rise in indirect hemagglutination antibody (IHA) titers following infection, and some had demonstrable parasitemia. Of the 23 progeny, 2 were stillbirths and 2 died soon after birth, but only the one neonate born of a mother inoculated intrauterally succumbed to acute toxoplasmosis. No physical anomalies were observed in any of the progeny. The toxoplasms organism was not isolated from any of the placentas obtained nor from the cord blood. None of the tissues from the stillborn or infant monkeys that died were positive for toxoplasmosis by mouse inoculation. The live progeny were usually born with high IHA antibody titers which were usually soon lost, indicating presence of passively acquired maternal antibody. However, 2 babies, born of mothers infected with tissue cysts on day 79 and 149 of gestation, maintained moderate to high titers for about 8 and 19 months respectively, indicating that an active infection had taken place but no clinical disease was detected. Data obtained suggest that although certain developmental stages of the toxoplasma organism and of the fetus may favor the occurrence of congenital infection, very little neonatal disease results in this primate model.

Toxoplasmosis in a calf

Gross post mortem and histopathological changes are described in a calf with toxoplasmosis. The major pathological changes were restricted to the lungs and kidneys and comprised interstitial pneumonia with multifocal necrosis, and glomerular necrosis. Many pseudocysts were present in both organs. The calf had been in close contact with young cats, one of which was killed and examined and shown to have a high antibody titre to Toxoplasma gondii, although there was little histological evidence of infection. No antibodies to toxoplasma were detected in serum from the dam of the calf, and accordingly, it is suggested that the cat was the source of infection for the calf.

Epidemic toxoplasmosis associated with infected cats

In October, 1977, an outbreak of toxoplasmosis occurred in patrons of a riding stable in Atlanta, Georgia; 37 became ill with toxoplasmosis or had serologic evidence by indirect fluorescent-antibody test of acute infection with Toxoplasma gondii (titer greater than or equal to 1:4096 or a positive fluorescent-antibody test for toxoplasma antibodies). Forty-nine additional patrons did not become ill. Two of the three adult cats from the stable were seropositive for toxoplasma, which was also recovered from the tissues of two kittens and four mice trapped near the stable. Patrons who spent most of their time at the end of the stable where a cat had defecated had the highest incidence of infection. Patrons who attended the stable daily had a higher attack rate than those who attended less frequently. No common meals were consumed, and dietary histroy eliminated meat as the source of infection. The data suggest that toxoplasma oocysts were the source of the infection.

Diseases transmitted from pets to man: an evolving concern for veterinarians

Pets are not a major source of human infections but they can transmit certain diseases to man. This transmission usually is complex, requiring close contact with pets or their excretions and frequently involves a breach of sound hygienic practice. In some instances, pathogens of animal origin are acquired inadvertently because infectivity can persist after evidence of gross contamination has gone. Veterinarians participate in controlling zoonotic diseases by encouraging rabies vaccination and hygienic treatment of pet feces and urine, by supporting community efforts toward responsible pet ownership and by advising on precautions for handling sick animals. It is recommended that veterinarians discourage the keeping of wild or exotic animals as pets and excess fondling of pets (particularly by children and pregnant women). Clients and kennel workers should be advised to use caution with animals that have aborted.

[Epidemiology of toxoplasmosis in Costa Rica: the importance of domestic rodents]

A positive dye test for Toxoplasma antibodies was observed in 5% of 100 mice (Mus musculus) and 30.4% of 23 rats (Rattus norvegicus and R. rattus). The parasite was isolated from two mice. The animals were captured in several urban localities in the metropolitan area of San José, Costa Rica. The number of positive animals found appears to be enough to infect cats, whose principal source of infections are the Toxoplasma cysts in the rodents. Therefore it is apparent that domestic mice and rats, besides the felines play an important role in the epidemiology of Toxoplasmosis in Costa Rica. Additional studies showed that the presence of Eimeria falciformis, a common coccidian in domestic mice, did not inhibit the Toxoplasma infections in these rodents.

Occurrence and attempted transmission of Toxoplasma gondii in European starlings (Sturnus vulgaris)

Serums of 563 fledgling starlings (Sturnus vulgaris) trapped during a 14 month period near Lodi, California were examined for antibodies to Toxoplasma gondii using the microtiter indirect hemagglutination method. Titers ranging from 1:64 to 1:512 were found in 4.8% of the birds. Starlings collected during May through October had a higher prevalence of antibody than those collected during November through April. Rats inoculated with individual heart and brain suspensions from 10 seropositive starlings remained seronegative for T. gondii antibodies when tested at 22 and 82 days post-inoculation. Peritoneal smears made from these rats at post-inoculation day 82 were negative for T. gondii.

Some aspects of the pathogenesis and comparative pathology of toxoplasmosis

Some aspects of the pathogenesis and comparative pathology of toxoplasmosis are described. The general pattern of infection, with or without necrosis, and tissue cyst formation as it occurs in all species is dealt with. The wide pathological manifestations of toxoplasmosis as seen in sheep, cattle, pigs, horses, dogs, cats, chinchillas and man are reviewed.

[Toxoplasmosis and contact with animals: study of 390 cases]

Three hundred and ninety patients with suspected toxoplasmosis due to their contact with animales--they owned them, or work with them--are studied. The great significance of this way of acquiring the disease is stated. Every patient had a complement fixation test and an intradermal reaction test with toxoplasmine. An 85.2% positiveness to complement fixation, and a 64.1% to intradermal test were found among those patients who informed animal contact; a 70,6% positiveness to complement fixation, and a 56,2% to intradermal reaction was found in the patients who denied having any contact with animals. This showed both the importance of animal contact as well as other forms of transmission. The contacts were also studied, and the animals were classified according to J. Jira, the researcher: maximal, high, minimal and unreceptiveness to toxoplasma. The possibility of acquiring toxoplasmosis from other sources besides the close contact with animals must be taken into consideration.

Attempted transmission of Toxoplasma gondii infection from pregnant cats to their kittens

Sixteen 1- to 7-week-old pregnant specific-pathogen free cats were inoculated orally with Toxoplasma gondii cysts. Fetuses and neonatal kittens were examined for toxoplasma infection by inoculating suspensions of their tissues into mice. Toxoplasma gondii was not isolated from 23 fetuses and 16 newborn kittens from 13 queens. Six (3 litters) of the 15 kittens from the 3 remaining queens were killed on the day of or a day after birth, and the remaining 9 kittens were housed with their mothers for 7 to 33 days. None of the 9 kittens from the 2 litters examined between 0 and 33 days of age was infected with T gondii. In the other litter, T gondii was isolated from 3 kittens killed at 9, 16, and 22 days of age but not from 3 littermates killed on days 1, 1, and 22. Internal organs from the 3 kittens with proved toxoplasma infectivity in mice were examined histologically. Multifocal granulomatous encephalitis, hepatitis, nephritis, myocarditis, myositis, and interstitial pneumonia were found in all 3 kittens. Toxoplasma forms were demonstrated histologically in the tissues of 2 of these kittens. The mode of toxoplasma infection in newborn kittens was not determined but did not appear to be either transplacental or via fecal contamination from oocysts excreted by the mother cat. Evidence obtained in these experiments suggests that transplacental toxoplasma infection in the cat is not an important epidemiologic factor in perpetuation of the disease in the feline population.

Attempeted transmission of feline coccidia from chronically infected queens to their kittens

Eight female, 12- to 34-month-old, specific-pathogen free cats were inoculated orally with Toxoplasma gondii cysts on day 0, then with Isospora felis and Isospora rivolta oocysts on day 39, and cysts of Hammondia hammondi on day 86 after inoculation with Toxoplasma. All cats shed oocysts of all 4 of these coccidia within 11 postinoculation days. The female cats were caged with 4 male Toxoplasma-free cats, starting 66 days after inoculation with Toxoplasma, until they were 5 to 6 weeks pregnant. Kittens that were born were housed with their mothers until necropsied or weaned. One 42-day-old kitten shed T gondii oocysts in feces. It was necropsied 2 days later and asexual stages of Toxoplasma (types D and E), gametocytes, and oocysts were demonstrated in sections of superficial epithelial cells of its small intestine. Lesions or forms of Toxoplasma were not demonstrated histologically in tis extraintestinal organs. Toxoplasma was not isolated from feces or tissues of the remaining 47 kittens born to these 8 queens. Toxoplasma was not isolated from the 4 male cats that were caged with infected females for 53, 59, 217, and 217 days. The source of toxoplasma infection in the kitten remained unknown but was considered unlikely to be congenital or through fecal contamination. Oocysts of I felis, I rivolta, and H hammondi were not found in the feces of any kittens, indicating that these coccidia are unlikely to be transmitted congenitally.

Tazonomy of Toxoplasma

After reviewing reports of the hosts, structure and life cycle of Toxoplasma, the genus is placed in the apicomplexan family Eimeriidae and the folllowing 7 species are recognized: Toxoplasma gondii (Nicolle & Manceaux) (type species) from about 200 species of mammals and birds, with oocysts in felids; Toxoplasma alencari (Da Costa & Pereira) from the frog Leptodactylus ocellatus; Toxoplasma brumpti Coutelen from the iguana Iguana tuberculata; Toxoplasma colubri Tibaldi from the snakes Coluber melanoleucus and Coluber viridiflavus; Toxoplasma hammondi (Frenkel & Dubey) (a new combination for Hammondia hammondi) from the house mouse with oocysts in the domestic cat; Toxoplasma ranae Levine & Nye from the leopard frog Rana Pipiens; and Toxoplasma serpai Scorza, Dagert & Iturriza Arocha from the toad Bufo marinus.

Toxoplasmosis in sheep. Epidemiological studies in flocks with reproductive loss from toxoplasmosis

The epidemiology of toxoplasmosis was studied in 51 flocks with reproductive loss from the infection. Overt toxoplasmosis was diagnosed on 2–4 neighbouring farms on 6 occasions, involving a total of 15 flocks. In 14 of the 51 flocks the frequency of abortion was highest in a definite part or age group of the flock.

Evidence was found that the source of infection may be confined to a particular part of an area or of a farm. There was apparently no transmission of Toxoplasma gondii from sheep with overt or latent toxoplasmosis to susceptible sheep. There were good reasons to believe that the parasite might have been transmitted via the silage in 1 of the flocks.

Feline toxoplasmosis from acutely infected mice and the development of Toxoplasma cysts

The development of Toxoplasma cysts was studied in mice inoculated with tachyzoites by several routes. After 1-30 days of infection, murine tissues were examined microscopically and portions or whole carcasses were fed to mice and cats. The feces of the cats were examined for oocyst shedding. Cyst-like structures containing distinct PAS-positive granules were first seen after 3 days of infection with tachyzoites, and became numerous by 6 days. Argyrophilic walls were first seen after 6 days, and became numerous by 16 days of infection with tachyzoites. Prepatent periods to oocyst shedding (PPO) were either "short" (3-10 days) or "long" (19-48 days). The "short" PPO was found only in cats that had ingested mice infected for 3 days or longer, and was related to the development of PAS-positive granules in T. gondii, and to high, 60-100%, oral infectivity rates for cats. The "long" PPO followed the ingestion of mice infected for only 1-2 days, and was related to tachyzoites without distinct PAS-positive granules and low, 32% or less, infectivity for cats. The "long" PPO followed also the ingestion of oocysts and the parenteral inoculation of tachyzoites, bradyzoites, or sporozoites. Using the "short" PPO as a criterion for detecting cysts in tissues, it was shown that (a) numerous cysts developed in mice 5 days after inoculation with tachyzoites, 7-9 days after inoculation with cysts, and 9-10 days after inoculation with oocysts, and (b) cysts developed faster and more frequently in the brain and muscle than in lungs, liver, spleen, and kidneys of mice inoculated with tachyzoites.

Acquired toxoplasmic chorioretinitis

A patient developed an acquired toxoplasmic chorioretinitis 11 days after exposure to infected animals. As systemic manifestations of the disease, the patient had rhinitis, sore throat, muscular pains, fatigue, cervical lymphadenopathy, and cardiac symptoms, with highly elevated Toxoplasma antibody titers. During treatment with prednisone, the chorioretinal lesion progressed to the macular area, but improvement was seen when pyrimethamine and sulfonamide therapy was started. The importance of this case relates to the unusual occurrence of acquired infection with systemic manifestations in toxoplasmic chorioretinitis and to the possibility of the transmission of toxoplasmosis by trophozoites in excretions.

Toxoplasmosis as a public health hazard

Recent advances in the epidemiology and life cycle of toxoplasmosis are reviewed. Cats play a key role. Toxoplasma has a coccidian-type entero-epithelial cycle with oocyst prodlction in the feline host. An extra-intestinal cycle occurs in both feline and non-feline hosts. The worldwide distribution and the public health significance of toxoplasmosis as a zoonosis is discussed, with particular reference to available data regarding Southern Africa.

[A comparative study of the role of domestic cats and dogs in the epidemiology of toxoplasmosis]

A total of 2643 persons in 5 different regions were examined for toxoplasmosis by the immunofluorescence test and toxoplasmin skin test. The presence in the house of cats and dogs was taken into account. In two of the five regions under study there was revealed an increased incidence of toxoplasmosis in persons keeping cats; this confirmed the role of these animals as a source of toxoplasmosis infection. The absence of such increase in the incidence of the disease in other regions in explained by the character of buildings admitting migration of cats or the presence in the given region of other active sources of infection. Toxoplasmosis incidence in persons who kept or didn't keep dogs displayed no significant difference.