Occurrence and first multilocus microsatellite genotyping of Neospora caninum from naturally infected dogs in dairy farms in Henan, Central China

Molecular Detection and Genotyping of Toxoplasma gondii and Neospora caninum in Slaughtered Goats in Central China

Toxoplasma gondii and Neospora caninum infections can cause reproductive failure in animals, including goats, and toxoplasmosis is one of the most important foodborne diseases. However, information on the molecular prevalence and genetic characterization of T. gondii and N. caninum in the tissues of goats in China is limited. In this study, brain samples of 422 slaughtered goats were collected from slaughterhouses in Henan and Anhui provinces, Central China, and examined for the presence of T. gondii and N. caninum by nested polymerase chain reaction (PCR) based on B1 and NC5 genes, respectively. The prevalence of T. gondii and N. caninum DNA was 5.2% and 2.8%, respectively. No significant differences were found between the prevalences of two parasite infections and animal age, sex, and region (p > 0.05). Two of 22 T. gondii-positive samples were completely genotyped at 11 genetic markers (SAG1, [3' + 5'] SAG2, alternative SAG2 [alt. SAG2], SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico) using PCR-restriction fragment length polymorphism, and were identified as genotype ToxoDB no. 225, which has not been previously reported in goats in any country worldwide. For N. caninum, two different sequences at the ITS1 region, three genotypes at the MS5 microsatellite locus, and one genotype at the MS8 locus were identified. This study showed that T. gondii and N. caninum are moderately prevalent in goats in Central China; however, it should be emphasized that T. gondii prevalence in goats poses a potential health threat for consumers in the investigated areas. To the best of our knowledge, this is the first report on the genetic characterization of N. caninum isolates from goats in China. Our results have important implications for a better understanding of the genetic diversity of these parasites in China.

Occurrence and genetic characterization of Toxoplasma gondii and Neospora caninum in slaughtered domestic rabbits in central China

Currently, information on the occurrence and genetic characterization of Toxoplasma gondii and Neospora caninum in tissues of rabbits in China is lacking. In this study, brain and heart samples from 470 slaughtered domestic rabbits were collected in Henan Province, Central China. The occurrence rate of T. gondii and N. caninum DNA detected by nested PCR was 2.8% and 2.1%, respectively. There were no significant differences (p > 0.05) in the frequency of the two parasite infections in relation to sex, breed, and region. Three out of 13 T. gondii-positive samples were completely or partially genotyped at 11 genetic markers using PCR-RFLP, and one was identified as ToxoDB genotype #9. For N. caninum, three different sequences at the ITS1 region and two genotypes at the MS5 microsatellite locus were identified. To our knowledge, this is the first genetic characterization of N. caninum isolates from rabbits.

Microsatellite Analysis of Geographically Close Isolates of Cystoisospora suis

Microsatellites are short repetitive DNA sequences of 2–6 repeats interspersed in the genome that display a rapid mutation rate and consequently show high variation between individuals or populations. They have been used to characterize population diversity and structure and the level of variation between different isolates of a number of different organisms, including apicomplexan protozoa. Currently nothing is known about the genetic variability and population structure of Cystoisospora suis (Apicomplexa: Coccidia), the causative agent of piglet coccidiosis, and we made use of the recently available genome of C. suis (strain Wien-I) to amplify microsatellite regions (ca. 300–550 bp) and evaluate the applicability of fluorescence-labeled primers to investigate amplicon length variation at high resolution using capillary electrophoresis (CE). Two phenotypically characterized isolates (Wien-I, toltrazuril susceptible; Holl 1 toltrazuril resistant) and six field isolates from Europe were compared by conventional PCR followed by agar-gel electrophoresis, Sanger sequencing, and CE (fluorescence labeling and fragment length analysis) to evaluate the applicability of the method. Four primer pairs could be identified that amplified bands of the expected size and were labeled for CE analysis. High resolution CE for size determination of PCR amplicons proved to be a reliable and simple method. It revealed high diversity of the analyzed strains, with marked differences even between two strains from neighboring swine farms. In follow-up studies, adaptation of the PCR assay to multiplexing and amplification of small DNA quantities will provide a cost-effective tool to analyse field strains to reveal geographic diversity that could be mapped to phenotypic traits.

A novel recombinase polymerase amplification (RPA) assay for the rapid isothermal detection of Neospora caninum in aborted bovine fetuses

The development of a method to rapidly diagnose Neospora caninum infection is highly desirable. Recombinase polymerase amplification (RPA), combined with lateral flow (LF) strips, is a novel approach to rapidly amplify and visualize DNA. We have developed a prototype LF-RPA assay, using primers and a probe that targeted a specific sequence in the N. caninum NC-5 gene. The N. caninum-specific LF-RPA assay was first tested on purified DNA from oocysts and amplified N. caninum DNA to detectable levels in 10 min, at a constant temperature and without the need for an expensive thermocycler. The designed RPA primers and probe displayed 100% specificity for detecting N. caninum without any cross-reaction with DNA from nine related protozoan spp. (eg Toxoplasma gondii, Sarcocystis gigantean, Sarcocystis zuoi, Hammondia hammondi, Hammondia heydorni, Eimeria cylindrica, Plasmodium falciparum, Theileria annulata and Babesia bigemina). Although, LF-RPA assay detected amounts as low as 50 fg of N. caninum DNA, it was nearly 5-fold less sensitive than previously published qPCR and nested PCR assays. We tested the diagnostic performance of the LF-RPA assay for the detection of N. caninum DNA in aborted bovine fetal tissue samples, and compared the results with those obtained from nested PCR. Out of the 75 samples examined, 18 (24%) and 17 (22.6%) tested positive using LF-RPA and nested PCR, respectively. Our results indicate that LF-RPA is a suitable assay for the rapid and reliable detection of N. caninum.

Neospora caninum oocyst shedding in a naturally infected dog from Italy

Although the seroprevalence of Neospora caninum infection in dogs can be relatively high, there are few reports of dogs naturally shedding N. caninum oocysts. Worldwide, the prevalence of Neospora excretion in canine faeces ranges from 0.03% to 4.9%. A mixed-breed male household dog of about 8years in age living in the district of Pisa (Tuscany, Central Italy) was referred for dysorexia, weakness and general lymph node enlargement. Clinical pathology demonstrated mild normocytic and normochromic anemia, thrombocytopenia and hypoproteinemia with hypoalbuminemia. Serology for Leishmania, Ehrlichia canis and Anaplasma phagocytophilum was negative. From lymph node and bone marrow analysis, T cell lymphoma, high grade, pleomorphic type, clinical stage V, was diagnosed. The dog was treated with a chemotherapy induction protocol with vincristine, cyclophosphamide, and prednisone for 8weeks. A faecal sample collected from the dog 7days after the beginning of the treatment and analysed by flotation test and a McMaster method, revealed the presence of 300 OPG N. caninum-like unsporulated oocysts of about 10-11μm in diameter. An aliquot of the same faecal sample analysed by PCR with species-specific primer pairs Np6+/Np21+ was positive for N. caninum DNA, while specific serology performed on sera collected at the first visit and a month later by IFAT, were positive with a titer of 1: 50 and 1:400, respectively. Soon after the dog died. Naturally occurring systemic illness or iatrogenic immunosuppression may predispose dogs to proliferation of the parasite. The dog was receiving chemo-immunosuppressive treatment for T cell lymphoma. For this reason it is possible to suppose that emission of Neospora oocysts in this dog was caused by reactivation of a latent infection.