Prevalence of Toxoplasma gondii Measured by Western Blot, ELISA and DNA Analysis, by PCR, in Cats of Western Mexico

Toxoplasma gondii is the causative agent of toxoplasmosis in humans and animals. The sexual reproductive cycle of Toxoplasma takes place in the small intestine of felines, the definitive hosts. In the final part of the sexual cycle, T. gondii forms oocysts in infected cats. Oocysts transferred via the faeces to the environment are highly infectious to both animals and humans. This study aimed to determine the prevalence and risk factors associated with T. gondii infection in cats from the metropolitan region of Guadalajara in western Mexico. Western blotting and ELISA for anti-Toxoplasma IgG antibodies was performed, and Toxoplasma DNA was identified using polymerase chain reaction. Prevalence of anti-T. gondii antibodies was 14.8% (44/297), and only 2/297 cases were positive for PCR. Cats older than one year were at an increased risk of infection (OR = 3.9, 95% CI 1.844–8.362). Sex, raw meat feeding, hunting habits, vaccination status, and body condition were not associated with positivity. The prevalence of T. gondii infection determined with Western blot in cats in the metropolitan area of Guadalajara, Jalisco, Mexico, was lower than that reported in previous studies.

Toxoplasma gondii infection in domestic and wild felids as public health concerns: a systematic review and meta-analysis

Felidae as definitive hosts for Toxoplasma gondii play a major role in transmission to all warm-blooded animals trough oocysts dissemination. Therefore the current comprehensive study was performed to determine the global status of T. gondii infection in domestic and wild felids aiming to provide comprehensive data of interest for further intervention approaching the One Health perspective. Different databases were searched by utilizing particular key words for publications related to T. gondii infecting domestic and wild feline host species, worldwide, from 1970 to 2020. The review of 337 reports showed that the seroprevalence of T. gondii in domestic cats and wild felids was estimated in 37.5% (95% CI 34.7-40.3) (I² = 98.3%, P < 0.001) and 64% (95% CI 60-67.9) (I² = 88%, P < 0.0001), respectively. The global pooled prevalence of oocysts in the fecal examined specimens from domestic cats was estimated in 2.6% (95% CI 1.9-3.3) (I² = 96.1%, P < 0.0001), and that in fecal samples from wild felids was estimated in 2.4% (95% CI 1.1-4.2) (I² = 86.4%, P < 0.0001). In addition, from 13,252 examined soil samples in 14 reviewed studies, the pooled occurrence of T. gondii oocysts was determined in 16.2% (95% CI 7.66-27.03%). The observed high rates of anti-T. gondii antibodies seroprevalence levels and oocyst excretion frequency in the felids, along with soil (environmental) contamination with oocysts may constitute a potential threat to animal and public health, and data will result of interest in further prophylaxis programs.

Toxoplasma gondii in Captive Wild Felids of Mexico: Its Frequency and Capability to Eliminate Oocysts

There is little information about Toxoplasma gondii in wild felids, even when these species have been associated with cases of toxoplasmosis in humans. In this study, samples of serum and whole blood were collected from 42 felids from 10 different species, in 4 Mexican zoos. Stool samples from 36 animals were also collected, corresponding to 82% of the felids included in the study. Stool samples were used for the search of oocysts by light field microscopy and PCR. Serum samples were analyzed by indirect immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) and indirect fluorescent antibody test (IFAT). DNA samples were purified from whole blood and stool for the amplification of a fragment of the SAG1 gene of T. gondii by a nested PCR (nPCR). The seroprevalence of IgG anti-T. gondii-specific antibodies by means of the ELISA was 100% (42/42) and 52.4% (22/42) by IFAT. The titers obtained varied from 1:80 to 1:2560. DNA of T. gondii was detected in 9.5% (4/42) of the blood samples by using nPCR. No oocysts were observed in the stool samples analyzed by light field microscopy. However, the DNA of the parasite was identified in 14.3% (5/35) of the stool samples evaluated. These results indicate a high prevalence of T. gondii in the studied populations of wild felids in captivity, with evidence of parasitemia and elimination of few oocysts even in adult hosts.

Toxoplasmosis in Mexico: epidemiological situation in humans and animals

Toxoplasmosis is a parasitic disease widely distributed throughout the world, infecting a wide variety of animal species including humans. In Mexico, this parasite has been detected in different parts of the country, particularly in the tropical areas where the parasite can remain infective for long periods of time due to the environmental conditions (i.e. high temperature and humidity over the whole year). Several epidemiological studies have been conducted in both human and animal populations, but despite the wide distribution of the agent in the country, there is a significant lack of knowledge on the parasite transmission, treatment alternatives and control measures. The lack of feral cat populations and control measures in sites of meat production for human consumption are playing a role that has led to the wide spread of the disease in the country, particularly in tropical areas of Southeastern Mexico. For these reasons, this manuscript aims to review the published information on relevant epidemiological aspects of infection with T. gondii in humans and animals from Mexico.

High Seroprevalence of Toxoplasma Gondii Infection in Female Sex Workers: A Case-Control Study

Through an age- and sex-matched case-control study, we sought to determine whether female sex workers have an increased risk of Toxoplasma gondii exposure and to determine the sociodemographic, work, clinical, and behavioral characteristics of these workers associated with T. gondii exposure. Female workers (n = 136) and controls (n = 272) were examined with enzyme-linked immunoassays (EIA) for the presence of anti-Toxoplasma IgG and IgM antibodies. IgM positive sera were additionally tested with enzyme linked-fluorescence immunoassay (ELFA). Anti-T. gondii IgG antibodies were found in 21 (15.44%) of 136 cases and in 10 (3.67%) of 272 controls (OR = 4.05; 95% CI: 1.84–8.89; P = 0.0001). Anti-T. gondii IgG levels higher than 150 IU/ml were found in 13 (9.6%) of 136 cases and in 8 (2.9%) of 272 controls (P = 0.007). Anti-T. gondii IgM antibodies were found in two cases and in six controls by EIA, but all were negative by ELFA. T. gondii seropositivity was associated with being born out of Durango State (OR = 10.47; 95% CI: 2.9–36.8; P < 0.01), injuries during sex work (OR = 6.30; 95% CI: 1.1–33.7; P = 0.03), and soil contact (OR = 4.11; 95% CI: 1.2–14.0; P = 0.02). This is the first report of an association of T. gondii infection and female sex workers.

Lack of association between Toxoplasma gondii infection and occupational exposure to animals

The association of infection with Toxoplasma gondii and occupational exposure to animals has been scantly determined. We performed a case-control study with 200 subjects from Durango Province, Mexico, occupationally exposed to animals and 200 age- and gender-matched subjects without this occupation. Sera from all participants were analyzed for anti-T. gondii IgG and IgM antibodies using enzyme-linked immunoassays. The association of seroprevalence with sociodemographic, work, clinical, and behavioral characteristics in cases was determined. Cases and controls had similar frequencies of anti-T. gondii IgG antibodies (12/200: 6.0% and 11/200: 5.5%, respectively) (OR = 3.0; 95% CI: 0.12-73.64; P = 1.0). The frequency of sera with high (>150 IU/ml) levels of anti-T. gondii IgG antibodies was comparable among cases and controls (P = 0.61). Seroprevalence of anti-T. gondii IgM antibodies was similar in cases (4, 2.0%) than in controls (4, 2.0%) (P = 1.0). Multivariate analysis showed that seropositivity was associated with eating while working (OR = 7.14; 95% CI: 1.91-26.72; P = 0.003) and consumption of duck meat (OR = 5.43; 95% CI: 1.43-20.54; P = 0.01). No association between seropositivity to T. gondii and occupational exposure to animals was found. However, risk factors for infection found should be taken into account to reduce the exposure to T. gondii.

Regional seroprevalence of Toxoplasma gondii antibodies in feral and stray cats (Felis catus) from Tasmania

Toxoplasma gondii is a cosmopolitan protozoan parasite of felids that also has significant implications for the health of wildlife, livestock and humans worldwide. In Australia, feral, stray and domestic cats (Felis catus) are the most important definitive host of T. gondii as they are the only species that can excrete the environmentally resistant oocysts that provide a major source of infection for mammals and birds. In Tasmania, the rapid decline of the Tasmanian devil (Sarcophilus harrisii) may allow an increase in feral cat abundance, thereby increasing the risk of T. gondii infection to a range of susceptible wildlife species. At present, there is scant information on the prevalence of T. gondii infection in feral cat populations across Tasmania. We tested feral cats from 13 regions across Tasmania for the presence of T. gondii–specific IgG antibodies using a modified agglutination test. Results were combined with serosurveys from three previous studies to enable a comparison of seroprevalence among 14 regions across Tasmania. We found that 84.2% (224 of 266) of cats tested positive for T. gondii IgG antibodies. This is among the highest rates of prevalence recorded from Australia, and significantly higher than for most other countries. Adult cats had higher seroprevalence than kittens but there was no difference between sexes. In Tasmania, seroprevalence was high in 12 of 14 regions (range: 79.3–100.0%), with only two regions (Tasman Island and Southern Tasmania) recording significantly lower seroprevalence (≤50%). This suggests a high risk of infection across Tasmania, and has significant implications for wildlife conservation should feral cat abundance increase with the ongoing declines in Tasmanian devils.

Seroprevalence of Toxoplasma gondii infection in domestic rabbits in Durango State, Mexico

There is a lack of information concerning the seroprevalence of Toxoplasma gondii infection in rabbits in northern Mexico. Through a cross sectional study, antibodies to T. gondii were determined in 429 domestic rabbits in Durango State, Mexico using the modified agglutination test. Rabbits were raised in 29 properties in 6 municipalities. Overall, antibodies to T. gondii were found in 70 (16.3%) of 429 rabbits, with titers of 1:25 in 42, 1:50 in 19, 1:100 in 5, 1:200 in 3, and 1:800 in 1. Seropositive rabbits were found in 21 (72.4%) of 29 properties, including 16 of 21 homes, 4 of 5 farms, and 1 of 3 pet shops. This is the first study of T. gondii infection in rabbits in Durango, Mexico. Results indicate that infected rabbits are a potential source of T. gondii infection in humans in Durango State.

Seroprevalence of Toxoplasma gondii infection in domestic horses in Durango State, Mexico

The seroprevalence of Toxoplasma gondii infection in horses in Mexico is unknown. Therefore, antibodies to T. gondii were assessed in 495 horses in Durango State, Mexico, using the modified agglutination test (MAT). Horses were from 18 farms in 3 municipalities in the valley region of Durango State. Antibodies to T. gondii were found in 30 (6.1%) of 495 horses, with MAT titers of 1:25 in 19, 1:50 in 6, and 1:100 in 5. Seropositive horses were found in 8 (44.4%) of 18 farms sampled in all 3 municipalities. Age, gender, and breed of horses did not influence significantly the seroprevalence of T. gondii infection. The seroprevalence in horses was higher in rural (7.8%) versus urban (0%) areas, and in larger herds (30-64 horses, 7.8%) versus smaller ones (3-28, 3.5%). The seroprevalence was higher in stall fed (16.5%) than in pastured horses (3.1%). Results indicate that infected horses represent a potential source of T. gondii infection for humans in Mexico. This is the first report of T. gondii infection in horses in Mexico.

Seroepidemiology of Toxoplasma gondii infection in elderly people in a northern Mexican city

Whereas it is well-known that the seroprevalence of infection with Toxoplasma gondii increases with age, details of the seroepidemiology of infection in elderly people are largely unknown. Anti-T. gondii IgG and IgM antibody levels were determined in 483 subjects aged ≥60 years old in Durango City, Mexico, using enzyme-linked immunosorbent assays. Socio-demographic, clinical, and behavioral characteristics from each participant were also obtained. In total, 58 (12%) of 483 participants (mean age 70.35±6.63 years) had anti-T. gondii IgG antibodies, and 14 (2.9%) also had anti-T. gondii IgM antibodies. Seroprevalence of infection varied significantly with age, birthplace, and educational level. Seroprevalence increased with age, especially in women (p=0.01), and was higher in subjects born outside of Durango State than those born within Durango State (p=0.008). Seroprevalence was higher in men with up to 12 years of education than in men with more than 12 years of education (p=0.01). Multivariate analysis of behavioral data showed a positive association of T. gondii infection with the presence of cats in the neighborhood, as well as consumption of boar, pigeon, iguana, and armadillo meats, and chorizo. Gender-specific analysis showed the described associations in women but not in men. In contrast, consumption of beef showed a negative association with T. gondii infection. This is the first report of the seroprevalence and contributing factors for T. gondii infection in elderly people, and of an association of the consumption of armadillo and iguana meats with T. gondii infection. Our results will provide the basis for the design of optimal preventive measures against T. gondii infection.

Seroprevalence of Toxoplasma gondii infection in domestic sheep in Durango State, Mexico

The seroprevalence of Toxoplasma gondii infection in sheep (Ovis aries) in northern Mexico is largely unknown. Antibodies to T. gondii were determined in serum samples from 511 sheep from 8 farms in Durango State, Mexico, using the modified agglutination test (MAT). Sheep were raised in 3 geographical regions, i.e., mountainous (n  =  68), semi-desert (n  =  132), and valley (n  =  311). Overall, T. gondii antibodies were found in 77 (15.1%) of 511 sheep, with MAT titers of 1∶25 in 27, 1∶50 in 10, 1∶100 in 11, 1∶200 in 11, 1∶400 in 8, 1∶800 in 3, 1∶1,600 in 4, and 1∶3,200 in 3. The seroprevalence of T. gondii infection increased significantly with age, indicating post-natal transmission. In contrast, gender, breed, flock size, and geographic region did not significantly influence the seroprevalence. Seropositive sheep were found in 7 of 8 farms sampled. This is the first report of T. gondii infection in sheep in Durango State, Mexico. Results indicate that infected sheep are probably an important source of T. gondii infection for humans in Durango State.

Seroprevalence of Toxoplasma gondii infection in domestic goats in Durango State, Mexico

Little is known concerning the seroprevalence of Toxoplasma gondii infection in goats in Mexico. Antibodies to T. gondii were determined in 562 goats in Durango, Mexico using the modified agglutination test. Goats were raised in 12 farms in two geographical regions: semi-desert (n=70) and mountains (n=492). Overall, antibodies to T. gondii were found in 174 (31%) of 562 goats, with titers of 1:25 in 18, 1:50 in 12, 1:100 in 10, 1:200 in 30, 1:400 in 32, 1:800 in 40, 1:1600 in 17, and 1:3200 or higher in 15. Seroprevalence of T. gondii increased with age, and varied with breed and geographic region; goats raised in the semi-desert region (Nubian breed) had a significantly higher seroprevalence (32.7%) than those raised in the mountains (mixed breed) (18.6%). Seropositive goats were found in all 12 (100%) farms sampled. This is the first report of T. gondii infection in goats in Durango State, Mexico. Results indicate that infected goats are likely an important source of T. gondii infection in humans in Durango State.

Seroprevalence of Toxoplasma gondii infection in domestic pigs in Durango State, Mexico

Little is known concerning the prevalence of Toxoplasma gondii infection in pigs in Mexico. Accordingly, antibodies to T. gondii were determined in 1,074 domestic pigs in Durango, Mexico using the modified agglutination test. Two groups (A, B) of pigs were sampled: Group A pigs (n  =  555) were raised in 3 geographical regions in Durango State and Group B pigs (n  =  519) were from Sonora State but slaughtered in Durango City. Overall, antibodies to T. gondii were found in 136 (12.7%) of 1,074 pigs with titers of 1∶25 in 29, 1∶50 in 23, 1∶100 in 18, 1∶200 in 22, 1∶400 in 12, 1∶800 in 8, 1∶1,600 in 2, and 1∶3,200 or higher in 22. Of the pigs raised in Durango State, seroprevalence varied with age, management, and the geographic region; pigs raised in backyards in the mountainous region had a significantly higher seroprevalence (32.1%) than those raised in the valley (13.0%) and the semi-desert regions (14.0%). In Group A pigs from Durango, seroprevalence of T. gondii infection was significantly higher in pigs older than 8 mo (19.5%) than in younger pigs (10.9%). In the whole pig population (Groups A and B together), seroprevalence was higher in pigs raised in Durango (16.0%) than in those raised in Sonora (9.1%) and higher in mixed-breed pigs (15.7%) than in pure-bred pigs (10.3%). This is the first, in-depth study on the seroprevalence of T. gondii infection of pigs in Mexico and the first report on pigs from Durango State, Mexico. Results indicate that infected pork is likely an important source of T. gondii infection for humans in Durango State.

Waterborne toxoplasmosis--recent developments

Humans become infected with Toxoplasma gondii mainly by ingesting uncooked meat containing viable tissue cysts or by ingesting food or water contaminated with oocysts from the feces of infected cats. Circumstantial evidence suggests that oocyst-induced infections in humans are clinically more severe than tissue cyst-acquired infections. Until recently, waterborne transmission of T. gondii was considered uncommon, but a large human outbreak linked to contamination of a municipal water reservoir in Canada by wild felids and the widespread infection of marine mammals in the USA provided reasons to question this view. The present paper examines the possible importance of T. gondii transmission by water.