Prevalence of antibody to Toxoplasma gondii and Trichinella spp. in feral pigs (Sus scrofa) of eastern North Carolina

Feral pigs (Sus scrofa) survive in many climates, reproduce year-round, and are dietary generalists. In the United States, the size and range of the feral pig population has expanded, resulting in greater interaction with humans and domestic swine and increased potential for disease transmission. We conducted a serosurvey in feral pigs from eastern North Carolina to determine exposure to the zoonotic parasites, Toxoplasma gondii and Trichinella spp. Between September 2007 and March 2009, blood serum was collected from 83 feral pigs harvested at Howell Woods Environmental Learning Center, Four Oaks, North Carolina, USA. We used a modified agglutination test to test for T. gondii antibodies and an enzyme-linked immunosorbent assay to test for Trichinella spp. antibodies. The prevalences of antibodies to T. gondii and Trichinella spp. were 27.7% and 13.3%, respectively and 4% (n=3) had antibodies to both agents. We detected an increased risk of T. gondii antibodies with age, whereas the risk of exposure to T. gondii across years and between sexes was similar. In eastern North Carolina, feral pigs have been exposed to T. gondii and Trichinella spp. and may pose a health risk to domestic swine and humans.     

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.     

National seroprevalence of Toxoplasma gondii in pigs

Serum samples from 11,842 commercial pigs killed in 1983-1984 throughout the United States were tested for anti-Toxoplasma gondii antibodies by the agglutination test in dilutions of 1:25, 1:50, and 1:500. Anti-T. gondii antibodies were found in 23.9% of pigs. At dilutions of 1:25, 1:50, and 1:500, 13.5%, 6.9%, and 3.5% were serologically positive, respectively. The prevalence of anti-T. gondii antibodies was higher in breeder pigs (42%) than in market pigs (23%). These results indicate that anti-T. gondii antibodies are widespread in the national swine herd.     

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 in pigs from Vietnam

Pigs are considered an important source of Toxoplasma gondii infection for humans. Antibodies to T. gondii were determined in serum samples from 587 pigs from Vietnam using the modified agglutination test (MAT) and found in 160 of 587 (27.2%) pigs, with MAT titers of 1:25 in 32 pigs, 1:50 in 34 pigs, 1:100 in 33 pigs, 1:200 in 24 pigs, 1:400 in 21 pigs, 1:800 in 14 pigs, and 1:3,200 in 2 pigs. Antibodies (MAT 1:20 or higher) were found in 75 of 325 (23%) finishers, 63 of 207 (32.3%) sows, and 22 of 55 (40%) boars. Results indicate high prevalence of T. gondii infection in pigs in Vietnam. This is the first report of prevalence of T. gondii in pigs from Vietnam.     

Seroprevalence of Toxoplasma gondii infection in slaughtered pigs and cattle in Liaoning Province, northeastern China

Toxoplasmosis is an important food-borne parasitic disease. In the present study, the seroprevalence of Toxoplasma gondii infection in slaughtered pigs and cattle was surveyed in Liaoning Province, northeastern China in May and June 2011. In total, 1,164 porcine serum samples and 646 bovine serum samples were collected from 5 counties and examined for T. gondii antibodies by an indirect hemagglutination test. Antibodies to T. gondii were found in 12.0% (140/1,164) of pigs, with some regional differences. The highest prevalence of 14.4% (47/326) was found in Fuxin followed by 12.5% (62/497) in Jinzhou; overall, 6.0% (39/646) was observed in cattle but with no regional difference (P > 0.05). Prevalence of T. gondii infection in pigs was also significantly higher compared to cattle (P < 0.05). The results of the present study indicate that infection with T. gondii in pigs and cattle is widely spread in China including Liaoning Province, northeastern China, and is, therefore, of public health concern.     

Enzootic toxoplasmosis in sheep in north-central United States

Of 1,564 serum samples from adult ewes from 33 farms in Iowa, Minnesota, South Dakota, Kansas, and Nebraska where toxoplasmosis-induced ovine abortions had been diagnosed, 65.5% were found positive for Toxoplasma gondii antibodies using the modified agglutination test. Toxoplasma gondii antibody titers of ewes were: less than 64 (34.5%), 64 (14.9%), 256 (22.0%), 1,024 (14.5%), and greater than 4,096 (13.8%). Thus, 28.3% of sheep had high titers (greater than 1,024) indicating recently acquired T. gondii infection. On certain farms, up to 95% of ewes were seropositive. Prevalence of T. gondii antibodies increased with age of the ewe. Of 665 ewes, 53.6% of 1-yr-old ewes were seropositive (titers greater than 64) versus 75% of 5-yr-old ewes. Results indicate that T. gondii infection in sheep in the United States is widespread.     

High prevalence of viable Toxoplasma gondii infection in market weight pigs from a farm in Massachusetts

The ingestion of uncooked infected meat is considered important in the epidemiology of Toxoplasma gondii infection in humans and little is known of the prevalence of viable T. gondii in meat used for human consumption in the United States. In the present study, viable T. gondii was isolated from 51 out of 55 pigs destined for human consumption. Hearts and tongues (500 g) from fifty-five 6-mo-old pigs from a farm in Massachusetts were bioassayed for T. gondii by feeding them to T. gondii-free cats. Feces of these cats were examined for shedding of T. gondii oocysts. Fifty-one of 55 cats fed pig tissues each shed 25-810 million T. gondii oocysts in their feces. Two of these cats consumed tissues of pigs that were shown to be seronegative with the Sabin-Feldman dye test, the modified agglutination test, and the Western blot. Results indicate that until examination of meat for T. gondii infection is implemented in slaughterhouses, all meat should be cooked according to industry guidelines before human consumption.     

A field trial of the effectiveness of a feline Toxoplasma gondii vaccine in reducing T. gondii exposure for swine

A 3-yr field trial was conducted on 8 commercial swine farms in Illinois to determine the effectiveness of a feline Toxoplasma gondii vaccine in reducing the exposure of swine to T. gondii. A vaccine consisting of live bradyzoites of the mutant T-263 strain, capable of preventing oocyst shedding by cats, was used in this study. Each farm was visited 3 times in 1994, 3 times in 1995, and once in 1996. Cats were trapped and inoculated with the T-263 oral vaccine during 1994 and 1995. On each visit, the following samples were collected: blood from pigs, cats, and mice for detection of serum antibodies to T. gondii, feces from cats to detect oocysts, and heart and brain tissues from rodents to determine the presence of T. gondii tissue cysts. The modified agglutination test (MAT), with a positive titer set at the 1:25 dilution, was used to determine serum antibodies. At first capture, 72.6% (61/84) of juvenile cats and 32.6% (31/95) of adult cats had no detectable antibodies (seronegative), indicating no prior exposure to T. gondii when they received their first vaccine. Of these first-time seronegative cats, 58.1% (18/31) of adult and 45.9% (28/61) of juvenile cats were recaptured and received a second dose of vaccine. Changes in the prevalence of T. gondii infection were evaluated from the prevaccination (1992, 1993) to the postvaccination (1996) period. Eleven cats (5%) were detected shedding oocysts between 1994 and 1996, of which 10 (90.1%) shed during 1994. The last detection of oocyst shedding by cats was during the first farm visit in 1995. There was a significant decrease in T. gondii seroprevalence for finishing pigs (P < 0.05, Wilcoxon sign rank test). There was a positive correlation (Spearman's p = 1.0, P < 0.0001) between the change in prevalence in juvenile cats and the change in prevalence in finishing pigs. The seropositivity rate (MAT > or = 1:25) in mice among all farms decreased from 4% in 1992-1993 to 0% in 1996. The mean prevalence of T. gondii tissue cyst isolation for mice on all farms decreased from 1.1% in 1994, to 0.8% in 1995, and to 0.5% in 1996. The results of this study suggest that the reduced exposure of pigs to T. gondii was due to the administration of the T. gondii vaccine to cats.     

Prevalence of Toxoplasma gondii in slaughtered pigs in the state of Pernambuco, Brazil

The object of this study was to investigate Toxoplasma gondii antibodies and parasite DNA in pigs in the state of Pernambuco, Brazil. Blood samples were collected from 305 slaughtered pigs in 11 municipalities, and their sera were tested for T. gondii antibodies using the indirect fluorescent antibody test (IFAT, cutoff 1:64); 38 (12.5%) samples were positive. Attempts were made to detect T. gondii DNA in the heart tissue of seropositive pigs using the B 1 gene and PCR; 21 (55.2%) of the 38 hearts were positive. This is the first detection of T. gondii DNA in tissues of serologically positive swine in the State of Pernambuco, Brazil.     

Prevalence of agglutinating antibodies to Toxoplasma gondii in adult and fetal mule deer (Odocoileus hemionus) from Nebraska

Toxoplasma gondii is an apicomplexan parasite of mammals and birds. Herbivores acquire postnatal infection by ingesting oocysts from contaminated food or water. Toxoplasma gondii infection is common in white-tailed deer, Odocoileus virginianus, but little is known about the prevalence of infection in mule deer, O. hemionus. We examined sera from 89 mule deer from Nebraska for agglutinating antibodies to T. gondii using the modified direct agglutination test (MAT) with formalin-fixed tachyzoites as antigen. Thirty-one (35%) of the samples were positive at dilutions of > or = 1:25. Samples were examined from 29 fetuses from these mule deer and none were positive in the MAT. Sera from 14 white-tailed deer from Nebraska were also examined and 6 (43%) were positive for T. gondii. Samples were examined from 5 fetuses from these white-tailed deer and none was positive in the MAT. Our results in both deer species from Nebraska are similar to studies conducted in white-tailed deer from other regions of the United States. Our findings indicate that mule deer are frequently infected with T. gondii and that mule-deer meat may be a source of human infection.     

Serological survey of Toxoplasma gondii infection among slaughtered pigs in northwestern Taiwan

A serological survey of Toxoplasma gondii infection among slaughtered pigs in the largest slaughterhouse located in Taoyuan County of northwestern Taiwan was conducted using the latex agglutination (LA) test during 1998. The overall seroprevalence of T. gondii infection was 28.8% (32/111) with LA titers of 1:32 (6, 18.8%), 1:64 (10, 31.2%), 1:128 (9, 28.1%), 1:256 (6, 18.8%), and 1:512 (1, 3.1%). No significant difference (P > 0.05) in seroprevalence between male (28.6%, 20/70) and female (29.7%, 12/41) slaughtered pigs was observed. A decreasing trend in the seroprevalence among slaughtered pigs examined in the same slaughterhouse was observed because of a lower seroprevalence (P < 0.05) than that (44.4%, 128/288) previously reported about 10 yr ago using the LA test. Nevertheless, it is important to avoid eating raw or undercooked pork in order to prevent the acquisition of T. gondii infection among people in Taiwan.     

Seroprevalence of Toxoplasma gondii and Neospora caninum in slaughtered pigs in the Czech Republic

In the Czech Republic, sera from 551 clinically healthy adult slaughtered pigs (females, 6-8 months old) were collected during the first half of June in 2010. Sera were tested for Toxoplasma gondii-specific IgG antibodies by an enzyme-linked immunosorbent assay; samples with more than 50% S/P were considered as positive. The same samples were also analysed for Neospora caninum antibodies using a commercial competitive-inhibition enzyme-linked immunosorbent assay; samples with more than 30% inhibition were considered as positive. Antibodies against T. gondii were found in 198 pigs (36%) in all districts with prevalences ranging from 18% to 75%. Antibodies against N. caninum were found in 16 pigs (3%); positive animals were found in 4 districts with prevalences ranging from 1% to 20%. Indication of mixed infections (concurrent presence of both N. caninum and T. gondii antibodies) was found in 8 (1·5%) pigs. The results of our study indicate that pigs in the Czech Republic have a relatively high seroprevalence for T. gondii, while they have only a low seroprevalence for N. caninum. Therefore, natural infection with T. gondii seems to be very common in Czech pigs. It is the first evidence of N. caninum antibodies in pigs in the Czech Republic. These results complete data about N. caninum infection in pigs in Europe.     

Seroprevalence of Toxoplasma gondii infection in chickens in Durango State, Mexico

Little is known concerning the seroprevalence of Toxoplasma gondii infection in chickens (Gallus domesticus) in Mexico. Antibodies to T. gondii were determined in 519 chickens in Durango, Mexico using the modified agglutination test (MAT). Two groups (A, B) of chickens were sampled. Group A chickens (n = 51) were raised in backyards in 7 municipalities in 3 geographical regions in Durango State. Group B chickens were raised in farms in the Mexican States of Sinaloa (n = 289) and Nayarit (n = 179) but slaughtered in 2 abattoirs in Durango City. Overall, antibodies to T. gondii were found in 36 (6.9%) of 519 chickens, with MAT titers of 1∶25 in 22, 1∶50 in 8, 1∶100 in 2, 1∶200 in 3, and 1∶400 in 1. Seroprevalence of T. gondii increased significantly with age and was significantly higher in Group A chickens than in Group B chickens. In Group A chickens, a 25.5% seroprevalence of T. gondii infection was found. Seropositive chickens were found in all 7 municipalities sampled. In Group B chickens, the seroprevalence of T. gondii infection was 4.9%. This is the first report of T. gondii infection in chickens in Durango State, Mexico.     

Seroprevalence of Toxoplasma gondii in equids from Southern Spain

Antibodies to Toxoplasma gondii were determined in serum samples from 616 equids (454 horses, 80 mules and 82 donkeys) in a cross-sectional study of 420 herds in Andalusia (Southern Spain), the region with the highest number of equids in Spain. Antibodies to T. gondii were found in 10.8% horses, 15.0% mules and 25.6% donkeys by using the modified agglutination test (MAT) at a cut-off of 1:25. Herd seroprevalence for horses, mules and donkeys was 14.7% (48/327), 23.9% (11/46) and 34.0% (16/47), respectively, and 75 herds (17.8%) had at least one seropositive animal. Significant differences in T. gondii seroprevalence were observed among species, with donkeys having the highest seroprevalence and horses the lowest (P=0.04). Seroprevalence was significantly higher in herds with presence of domestic ruminants. This study is the first report of the presence of T. gondii antibodies in equine species in Spain and the first reporting T. gondii infection in donkeys in Europe. The presence of antibodies is indication of contact with the parasite and therefore, consumption of equine meat could be a potential source of human infection in Spain.     

Seroprevalence of Toxoplasma gondii in pigs, sheep, goats, and cattle from Grenada and Carriacou, West Indies

Prevalence of Toxoplasma gondii infection in pregnant women in Grenada is considered high. Little is known of the epidemiology of T. gondii infection in Caribbean Islands. Serum samples of 750 food animals in Grenada and Carriacou were tested for antibodies to T. gondii by the modified agglutination test (MAT). Antibodies to T. gondii (MAT, 1∶25 or higher) were found in 23.1% of 247 pigs, 44.1% of 204 sheep, 42.8% of 180 goats, and 8.4% of 119 cattle. Seroprevalence increased with age, indicating postnatal acquisition of T. gondii. Antibody titers of 1∶200 or higher were present in 65 of 90 seropositive sheep, 61 of 77 seropositive goats, and 23 of 57 seropositive pigs. However, none of the cattle had a MAT titer of 1∶200, suggesting that bovines are a poor host for T. gondii. Results indicate that pigs, sheep, and goats could be important sources of T. gondii infection if their meat is consumed undercooked.     

Seroprevalence of Toxoplasma gondii in harbor seals (Phoca vitulina) in southern Puget Sound, Washington.

As part of the Puget Sound Ambient Monitoring Program of the Washington Department of Fish and Wildlife, serum samples from 380 harbor seals (Phoca vitulina) were tested for antibodies to Toxoplasma gondii in the modified agglutination test (MAT) incorporating formalin-fixed tachyzoites and mercaptoethanol. Antibodies to T. gondii were found in 29 of 380 (7.6%) seals with titers of 1:25 in 13, 1:50 in 14, and > or = 1:500 in 2 seals. Results indicate natural exposure of these wild marine mammals to T. gondii oocysts.     

Seroprevalence of Toxoplasma gondii antibodies in cats and pigs from rural Western Amazon, Brazil

Antibodies to Toxoplasma gondii were assayed in sera of 63 cats and 80 pigs from 71 farms located at Rond?nia State, Western Amazon, Brazil, by the modified agglutination test (MAT) and the indirect immunofluorescent antibody test (IFAT). Antibodies (MAT > or = 1: 25) were found in 55 of 63 cats (87.3%) with titers of 1:25 in 2, 1:50 in 2, 1:100 in 7, 1:200 in 1, 1:400 in 2, 1:800 in 9, 1:1,600 in 6, and 1:3,200 or higher in 26 cats. By IFAT, antibodies were found in 55 cats (87.3%) with titers of 1:25 in 2, 1:50 in 1, 1:100 in 4, 1:200 in 4, 1: 400 in 1, 1:800 in 13, 1:1,600 in 12, and 1:3,200 or higher in 18 cats. In pig sera, by MAT, antibodies were found in 30 of 80 pigs (37.5%) with titers of 1:25 in 2, 1:50 in 3, 1:100 in 2, 1:200 in 8, 1:400 in 3, 1:800 in 5, 1:1,600 in 3, and 1:3,200 or higher in 4 pigs. By using the IFAT (titers > or = 1:64), antibodies were found in 35 (43.7%) pigs. The ingestion of undercooked tissues of infected pigs can be a source of T. gondii infection for humans and cats. However, the high seroprevalence of T. gondii in cats from the Amazon seems most likely to be indicative of high contamination of the environment by oocysts.     

Seroepidemiology of Toxoplasma gondii infection in human adults from three rural communities in Durango State, Mexico

There is scarce information concerning the epidemiology of Toxoplasma gondii infection in people of rural Mexico. Anti-T. gondii immunoglobulin (Ig)G and IgM antibodies were sought in 462 adult inhabitants from 3 rural communities of Durango, Mexico, using enzyme-linked immunoassays. In total, 110 (23.8%) of 463 persons had IgG anti-T. gondii antibodies. Ten (2.2%) of them also had IgM anti-T. gondii antibodies. Prevalences of T. gondii IgG antibodies in the 3 communities varied from 14.8 to 35.8%. The highest prevalence of infection was observed in participants older than 70 yr and in those with good housing conditions. Toxoplasma gondii infection was significantly associated with consumption of squirrel (adjusted odds ratio [OR] = 4.22; 95% confidence interval [CI] = 1.11-16.05) and turkey meat (adjusted OR = 4.58; 95% CI = 1.14-18.44). This is the first epidemiological study of T. gondii prevalence in rural Mexico.