Seroprevalences of Toxoplasma gondii and Neospora caninum in pet rabbits in Japan

Comparison of the performance of SAG2, GRA6, and GRA7 for serological diagnosis of Toxoplasma gondii infection in cats

Toxoplasmosis is an important zoonotic disease caused by Toxoplasma gondii that can infect almost all warm-blooded animals worldwide, including humans. The high prevalence of T. gondii infection and its ability to cause serious harm to humans and animals, especially immunodeficient individuals, make it a key public health issue. Accurate diagnostic tools with high sensitivity are needed for controlling T. gondii infection. In the current study, we compared the performance of recombinant SAG2, GRA6, and GRA7 in ELISA for the serological diagnosis of T. gondii infection in cats. We further investigated the antigenicity of recombinant dense granule protein 3 (rGRA3), rGRA5, rGRA8, and rSRS29A expressed in a plant-based, cell-free expression system for detecting antibodies in T. gondii-infected cats. In summary, our data suggest that GRA7 is more sensitive than the other two antigens for the serodiagnosis of T. gondii infection in cats, and GRA3 expressed in the cell-free system is also a priming antigen in serological tests for detecting T. gondii infection in cats.

Seroprevalence of Neospora caninum in pet cats, dogs and rabbits from urban areas of Poland

BACKGROUND

Neospora caninum (N. caninum) has a broad intermediate host range and might cause multisystemic lesions in various species of animals. Dogs are both intermediate and definitive hosts of the parasite and play a crucial role in the horizontal transmission of this protozoan to other animals. Cats and rabbits could be sensitive to infection with N. caninum, however, clinical symptoms and the exact route of infection in these species are unknown. The epidemiology of N. caninum in cats and rabbits has been barely researched, and there is no published record of the seroprevalence of N. caninum infection in these species in Poland. Thus, the present study aimed to determine the frequency of seroreagents for N. caninum within pet dogs, cats and rabbits from urban areas of Poland and to identify possible risk factors for these animals.

RESULTS

In total, serum samples from 184 cats (Felis catus), 203 dogs (Canis familiaris) and 70 rabbits (Oryctolagus cuniculus) were used in the study. The seroprevalence of anti-N. caninum antibodies in dogs and cats reached 1.0% (2/203; 95% CI: 0.3-3.5) and 3.3% (6/184; 95% CI: 1.5-6.9), respectively. No significant differences in seroprevalence regarding age group, gender, symptoms or sampling location were found. All 70 samples from pet rabbits were negative for anti-N. caninum antibodies.

CONCLUSIONS

The seroprevalence rates of N. caninum in dogs and cats in the present study were low, however, our results confirmed N. caninum circulates among dog and cat populations in Poland, and neosporosis should be included in the differential diagnosis of neuro-muscular disorders in these species. This is the first serological survey of N. caninum in European pet cats and rabbits. The role of pet rabbits in N. caninum epidemiology and circulation in Poland is marginal.

Seroprevalence of Encephalitozoon cuniculi and Toxoplasma gondii antibodies and risk-factor assessment for Encephalitozoon cuniculi seroprevalence in Finnish pet rabbits (Oryctolagus cuniculus)

Background

Neurological signs, such as head tilt, torticollis, paralysis, and seizures, are common in rabbits. Differential diagnoses include two zoonotic infections caused by the microsporidial fungi Encephalitozoon cuniculi and the apicomplexan protozoa Toxoplasma gondii. Both infections are mainly latent in rabbits but may cause severe or even fatal disease. Although several international studies have reported the seroprevalence of these pathogens in different commercial rabbit populations, similar prevalence studies and risk-factor analyses among family-owned pet rabbits are uncommon and lacking in Scandinavia. We sought to estimate the seroprevalence and possible risk factors for E. cuniculi and T. gondii among Finnish pet rabbits. We used ELISA to measure E. cuniculi IgG seroprevalence of 247 rabbits and modified direct agglutination test for T. gondii seroprevalence of 270 rabbits. Samples were collected as part of the Finnish Pet Rabbit Health Research project. Internet-based questionnaires (n = 231) completed by the rabbit owners were used for risk-factor analysis.

Results

The apparent seroprevalence of E. cuniculi was 29.2% and true seroprevalence of T. gondii 3.9%. Risk factors were analysed only for E. cuniculi due to the low T. gondii seroprevalence. The final multivariable logistic regression model revealed that rabbits spending the whole summer outdoors had a higher risk of being E. cuniculi seropositive than rabbits with limited outdoor access. Additionally, rabbits living in households with only one or two rabbits had higher risk of being E. cuniculi seropositive than those in multi-rabbit households.

Conclusions

Nearly one third of Finnish pet rabbits participating in this study had E. cuniculi IgG antibodies, indicating previous exposure to this pathogen. The prevalence is similar to that reported previously in clinically healthy rabbit populations in UK and Korea. While the seroprevalence of T. gondii was low (3.9%), antibodies were detected. Therefore, these zoonotic parasitic infections should be considered as differential diagnoses when treating rabbits.

Toxoplasma gondii in humans and animals in Japan: An epidemiological overview

Toxoplasmosis is a cosmopolitan protozoan zoonosis caused by Toxoplasma gondii infamous for inducing severe clinical manifestations in humans. Although the disease affects at least one billion people worldwide, it is neglected in many countries including developed ones. In literature, the epidemiological data documenting the actual incidence of the disease in humans and domestic animals from Japan are limited and importantly many earlier papers on T. gondii infections were published in Japanese and a considerable part is not available online. Herein, we review the current summary about the epidemiological situation of T. gondii infection in Japan and the potential associated risk factors in humans and animals as well as the different T. gondii genotypes isolated in Japan. Several T. gondii isolates have been identified among cats (TgCatJpTy1/k-3, TgCatJpGi1/TaJ, TgCatJpObi1 and TgCatJpOk1-4) and goats (TgGoatJpOk1-13). This literature review underscores the need for a nationwide investigation of T. gondii infection in Japanese people and assessment of the socioeconomic impact of the disease burden. Furthermore, epidemiological studies in domestic and wild animals and estimation of degree of contamination of soil or water with T. gondii oocysts are needed, for a better understanding of the scope of this public health concern.

Wild Rabbit Exposure to Leishmania infantum, Toxoplasma gondii, Anaplasma phagocytophilum and Babesia caballi Evidenced by Serum and Aqueous Humor Antibody Detection

Wild rabbits (Oryctolagus cuniculus) can be important sentinel species for the presence of zoonotic pathogens. Therefore, we collected blood samples from wild rabbits harvested by hunters during the hunting season 2019–2020 on the island of Lemnos, to determine exposure of wild rabbits to the zoonotic pathogens Leishmania infantum, Toxoplasma gondii, Anaplasma phagocytophilum and Babesia caballi, as well as aqueous humor to assess its diagnostic performance in terms of sensitivity, specificity, positive and negative likelihood ratios. Antibodies against these pathogens were detected by Indirect Immunofluorescence Antibody (IFA) assay. Out of the 72 wild rabbits included in the study, 4.2%, 5.5%, 18% and 9.7% were seropositive to L. infantum, T. gondii, A. phagocytophilum and B. caballi, respectively. Although less frequently, antibodies were also detected in aqueous humor of wild rabbits. The antibody detection in aqueous humor presented 100% specificity but decreased sensitivity compared to serum suggesting that aqueous humor could be successfully used in epidemiological studies to confirm exposure at the population level but has little diagnostic value at the individual level. This is the first report on the seropositivity of wild rabbits to A. phagocytophilum and B. caballi and the detection of antibodies against A. phagocytopylum, L. infantum, T. gondii and B. caballi in the aqueous humor.

Epidemiological and Public Health Significance of Toxoplasma gondii Infection in Wild Rabbits and Hares: 2010-2020

Toxoplasmosis is a zoonosis of global distribution, and Toxoplasma gondii infections are common in humans and animals worldwide. Hares and rabbits are important small game species, and their meat is consumed by humans in many countries. Demand for rabbit meat for human consumption is increasing; therefore, toxoplasmosis in rabbits and hares is of epidemiological significance. Viable T. gondii has been isolated from rabbits. The present review summarizes worldwide information on the seroprevalence, parasitological investigations, clinical cases, isolation, and genetic diversity of T. gondii in wild rabbits, free domestic rabbits, hares, and other rabbits from 2010 to 2020. Differences in prevalence, susceptibility, genetic variants, and clinical implications of T. gondii infection in rabbits and hares are discussed. This review will be of interest to biologists, parasitologists, veterinarians, and public health workers. Additional studies are needed to increase our knowledge of genetic variants and the population structure of T. gondii in rabbits and hares and to understand the differences in susceptibility to T. gondii in hares in different areas.

Characterization of a spontaneous cyst-forming strain of Toxoplasma gondii isolated from Tokachi subprefecture in Japan

Apicomplexan parasite Toxoplasma gondii has three distinct clonal lineages: high, medium and low virulent strains, type I, II and III, respectively. T. gondii avoids the immune response by transforming from fast multiplying tachyzoite to slow multiplying bradyzoite, and establishing a chronic infection. In the present study, we isolated a new strain of T. gondii from cat feces in the Tokachi subprefecture, Hokkaido, Japan and named it as TgCatJpObi1 (Obi1) strain. Genotyping analysis of 12 loci revealed atypical characters close to type II, genotype 4 according to ToxoDB classification. Phenotypically, Obi1 strain shows slow growth rate and the ability of spontaneous cyst formation in both human foreskin fibroblast (HFFs) and mouse peritoneal macrophages in vitro without bradyzoite induction. Parasite virulence was assessed by means of mouse survival upon infection with either Obi1 or ME49 strains. Obi1 strain displayed no mortalities in comparison to type II clonal lineage, ME49 at LD₅₀ to LD₁₀₀ range (1 × 10³-10⁶ tachyzoites). Although virulence of Obi1 strain is significantly lower than that of ME49, nucleotide sequences analyses revealed that genes of virulence factors such as Gra15, Rop5, 16, 17, and 18 in Obi1 strain were 100% identical to those in the type II strain. Thus, characterization of a newly isolated strain, Obi1, is crucial to clarify the development of toxoplasmosis in both humans and animals.

Evidence of infection with Toxoplasma gondii and Neospora caninum in South Australia: using wild rabbits as a sentinel species

OBJECTIVE

The aim of this study was to utilise wild rabbits (Oryctolagus cuniculus) as a sentinel species to study levels of environmental contamination with N. caninum and T. gondii in South Australia, and to examine associations with rainfall, climate and land use.

DESIGN

Toxoplasma gondii (T. gondii), an apicomplexan parasite, causes the clinical disease toxoplasmosis, which can affect sheep as well as humans and many other animals. Neosporosis, the clinical disease caused by closely related Neospora caninum (N. caninum), causes abortions in cattle, with large economic impacts to cattle industries.

METHODS

Aliquots of wild rabbit (Oryctolagus cuniculus) serum were obtained from twelve sites across South Australia over a period of eighteen years, with a total of 2114 samples. An in-house Modified Agglutination Test (MAT) was developed, and samples were screened for the specific antibodies against both T.gondii and N. caninum.

RESULTS

Overall, 9.9% of samples screened for T. gondii tested positive and 6.1% of samples screened for N. caninum tested positive. There was no difference observed in seroprevalence of T.gondii specific antibodies between samples collected throughout summer, autumn, winter or spring. By contrast, a significantly higher (p=0.030) seroprevalence of N. caninum specific antibodies was observed in spring than any other season. T. gondii and N. caninum antibodies were discovered at sites across a broad area of South Australia, indicating these environments maybe infected with both parasites.

CONCLUSION

Results provide evidence that suggests N. caninum oocysts may have different survival characteristics, such as varying tolerances to low relative humidity, than T. gondii oocysts.

Comparison of Seroprevalence and PCR Results in the Detection of Toxoplasma gondii in Pet Rabbits in Poland

Toxoplasma gondii infections are prevalent in humans and animals worldwide. The aim of the study was to estimate the seroprevalence of T. gondii in pet rabbits, as well the presence of T. gondii DNA in their blood. A total of 360 pet rabbits were investigated for the presence of antibodies and antigens of T. gondii in blood samples using a modified agglutination test (MAT) and nested PCR, respectively. Antibodies against T. gondii were found in 44 (12.12%) of pet rabbits. In rabbits that received unwashed vegetables 13.13% were positive for T. gondii antibodies, whereas all rabbits that received washed vegetables were seronegative. The prevalence of anti-T. gondii antibodies was statistically higher in samples collected from ill rabbits (45.45%) compared with healthy ones (8.87%), as well in the group of rabbits that had contact with cats (16.13%) compared with those without contact with cats (3.57%). The percentage of seropositive samples derived from all three sampling regions of Poland was as follows: Silesia (12.20%), Lower Silesia (6.09%), and Lesser Poland (18.03%). No statistical differences in seroprevalence were observed according to age or sex of rabbits. All tested blood samples were negative for the T. gondii B1 gene in nested PCR. This is the first study of seroprevalence and the presence of T. gondii in the blood of pet rabbits in Poland. Our study indicates that health status of rabbits, contact with cats, as well sampling region may have an important impact on the prevalence of T. gondii infection.

Dembo polymerase chain reaction technique for detection of bovine abortion, diarrhea, and respiratory disease complex infectious agents in potential vectors and reservoirs

Bovine abortion, diarrhea, and respiratory disease complexes, caused by infectious agents, result in high and significant economic losses for the cattle industry. These pathogens are likely transmitted by various vectors and reservoirs including insects, birds, and rodents. However, experimental data supporting this possibility are scarce. We collected 117 samples and screened them for 44 bovine abortive, diarrheal, and respiratory disease complex pathogens by using Dembo polymerase chain reaction (PCR), which is based on TaqMan real-time PCR. Fifty-seven samples were positive for at least one pathogen, including bovine viral diarrhea virus, bovine enterovirus, Salmonella enterica ser. Dublin, Salmonella enterica ser. Typhimurium, and Neospora caninum; some samples were positive for multiple pathogens. Bovine viral diarrhea virus and bovine enterovirus were the most frequently detected pathogens, especially in flies, suggesting an important role of flies in the transmission of these viruses. Additionally, we detected the N. caninum genome from a cockroach sample for the first time. Our data suggest that insects (particularly flies), birds, and rodents are potential vectors and reservoirs of abortion, diarrhea, and respiratory infectious agents, and that they may transmit more than one pathogen at the same time.

Clinical Signs, Diagnosis, and Treatment of Encephalitozoon cuniculi Infection in Rabbits

Central vestibular dysfunction caused by Encephalitozoon cuniculi frequently mimics the condition of a peripheral disorder. A negative antibody titer rules out E cuniculi as the cause of present clinical signs. Cerebrospinal fluid analysis including polymerase chain reaction is considered an inappropriate diagnostic method for in vivo diagnosis of encephalitozoonosis. The usefulness of glucocorticoid anti-inflammatories in the treatment of encephalitozoonosis is called into question. Encouraging activity early in the course of disease and adding in therapeutic exercise may represent the most important part of therapy in rabbits with vestibular dysfunction associated with encephalitozoonosis.

Prevalence of Toxoplasma gondii and other intestinal parasites in cats in Tokachi sub-prefecture, Japan

The present study investigated the prevalence of Toxoplasma gondii and other intestinal parasites in cats in the Tokachi subprefecture in Japan. A total of 365 household cats were included in the study, and 353 serum and 351 fecal samples were collected and analyzed. T. gondii IgG antibodies were detected in the sera of 16.14% of cats based on Latex agglutination test and ELISA. For ELISA, T. gondii RH strain tachyzoites lysate and T. gondii SAG2 recombinant protein were used as antigens. Low seropositivity was detected in cats younger than one year and older than 11 years; outdoor and hunter cats showed significantly high seropositivities. Neutering either in male or female cats, but not gender, had a considerable effect on seroprevalence. Toxoplasma gondii oocysts were detected in one fecal sample. The overall parasitic infestation in cats was 12.5%. Other detected parasites included Toxocara species, which showed the highest prevalence of 7.7%, followed by Isospora spp. (2%), Taenia spp. (1.7%), and Ancylostoma spp. (0.9%). Spirometra spp. was detected in only one sample. Outdoor cats comprised 50% of all 44 parasite-infested cats. Although T. gondii oocysts were detected in only one sample, the relatively high seroprevalence of T. gondii indicated that it can pose significant risks to the environment. Our findings highlighted the potential of outdoor cats as a source of T. gondii and other parasites.

Lactate dehydrogenase in Toxoplasma gondii controls virulence, bradyzoite differentiation, and chronic infection

In the asexual stages, Toxoplasma gondii stage converts between acute phase rapidly replicating tachyzoites and chronic phase slowly dividing bradyzoites. Correspondingly, T. gondii differentially expresses two distinct genes and isoforms of the lactate dehydrogenase enzyme, expressing LDH1 exclusively in the tachyzoite stage and LDH2 preferentially in the bradyzoite stage. LDH catalyzes the interconversion of pyruvate and lactate in anaerobic growth conditions and is utilized for energy supply, however, the precise role of LDH1 and LDH2 in parasite biology in the asexual stages is still unclear. Here, we investigated the biological role of LDH1 and LDH2 in the asexual stages, and the vaccine strain potential of deletion mutants lacking LDH1, LDH2, or both genes (Δldh1, Δldh2 and Δldh1/2). Deletion of LDH1 reduced acute parasite virulence, impaired bradyzoite differentiation in vitro, and markedly reduced chronic stage cyst burdens in vivo. In contrast, deletion of LDH2 impaired chronic stage cyst burdens without affecting virulence or bradyzoite differentiation. Deletion of both LDH1 and LDH2 induced a more severe defect in chronic stage cyst burdens. These LDH mutant phenotypes were not associated with any growth defect. Vaccination of mice with a low dose of mutants deleted for LDH elicited effective protective immunity to lethal challenge infection, demonstrating the vaccine potential of LDH deletion mutants. These results suggest that lactate dehydrogenase in T. gondii controls virulence, bradyzoite differentiation, and chronic infection and reveals the potential of LDH mutants as vaccine strains.

Age-specificity of Toxoplasma gondii seroprevalence in sheep, goats and cattle on subsistence farms in Bangladesh

Toxoplasma gondii is a zoonotic protozoan parasite that infects humans and domestic animals. In this study, the seroprevalence of T. gondii antibodies was investigated using serum samples collected from 83 sheep, 146 goats and 37 cattle from a dozen subsistence farms in Bangladesh. Fifty-eight out of 83 sheep (69.9%), 89 out of 146 goats (61.0%) and 10 out of 37 cattle (27.0%) were seropositive for the parasite. Seroprevalence in young goats (<1 year old) was significantly lower than that of the adult goats (>1 year old). In contrast, seroprevalence for young and adult sheep was similar. These results indicate that acquired infection with T. gondii occurs in this region of Bangladesh, at least among goats.