Chanya Kengradomkij

Antibody-ELISA for Trypanosoma evansi: Application in a serological survey of dairy cattle, Thailand, and validation of a locally produced antigen

Trypanosoma evansi is generally considered a mild pathogen in bovines. However, in Asia, acute and chronic signs have been observed in cattle, with high levels of parasitaemia, abortion and death. Investigations in Asian cattle are needed to better understand this epidemiological situation. To generate comparable data at a regional level, development and standardization of an antibody-enzyme linked immunosorbent assay for T. evansi (ELISA/T. evansi) was initiated and applied in an epidemiological survey carried out in dairy cattle in Thailand. A batch of 1979 samples was collected from dairy farms located throughout the countrys four regions. Soluble T. evansi antigens initially produced in France were also produced in Thailand for comparison and technology transfer. Screening of 500 samples allowed us to identify reference samples and to determine the cut-off value of the ELISA. Seropositive animals - some of them confirmed by PCR - were found in the four regions, in 12 out of 13 provinces, in 22 out of 31 districts, in 56 farms out of 222 (25%, 95%CI+/-6%) and in 163 animals out of 1979 (8.2, 95%CI+/-1.2%). Estimated seroprevalence in 35 farms ranged between 1% and 30%, and in 21 farms it was >30%. Approximately 25% of survey cattle were exposed to the infection, in various situations. A sub-sample of 160 sera was tested on both antigens. Wilcoxons (Z=1.24; p=0.22) and McNemarss tests (CHI2=3.55; p=0.09) did not show any significant differences, showing that the locally produced antigen is suitable for further evaluation in the surrounding countries. Use of this standardized serological method will broaden knowledge of the prevalence and impact of the disease at the regional level in South-East Asia. Further validation of this ELISA will be necessary in other host species such as buffalo, horse and pig.

Seroprevalence and risk factors associated with exposure of water buffalo (Bubalus bubalis) to Neospora caninum in northeast Thailand

Water buffalo are important draft animals for agriculture in resource-restricted areas worldwide. Water buffalo were shown to be experimentally susceptible to infection with Neospora caninum, potentially affected by neosporosis, and naturally exposed to the parasite in Asia. Although enzootic to Thailand, the distribution of N. caninum among Thai water buffalo is unclear. The objectives of this study were to determine the seroprevalence of N. caninum among water buffalo of northeast Thailand and to identify risk factors associated with their exposure to N. caninum. Sera from 628 water buffalo from 288 farms were tested with an indirect fluorescent antibody test (IFAT). A total of 57 samples from 48 herds contained antibodies to N. caninum, indicating overall seroprevalence of 9.1% and 16.7% among individual animals and herds, respectively. The overall seroprevalence was highest in provinces located in the Khorat Basin in the southern part of the region tested. Host age was also associated with seroprevalence, with the greatest seroprevalence (16.1%) among buffalo over 10 years of age, followed by 5-10 years of age (13.4%), 3-5 years (9.2%), and less than 3 years (1.2%). These results collectively suggested that horizontal transmission from canine definitive hosts was an important route of water buffalo exposure to N. caninum. These results also verified the importance of risk factor analysis for effective bovine neosporosis control strategies at the local level.

Prevalence and genotype of Giardia duodenalis in dairy cattle from Northern and Northeastern part of Thailand

Abstract The aims of this study were to determine prevalence and genotype of Giardia duodenalis in feces of dairy cattle from the northern part and the northeastern part of Thailand. A total of 900 fecal samples were collected directly from rectum and examined by using zinc sulphate centrifugal flotation technique and polymerase chain reaction (PCR). The overall prevalence of G. duodenalis in dairy cows was 5.0 % (45/900) by zinc sulphate centrifugal flotation and 6.0 % (54/900) by PCR. Genotypes of G. duodenalis found in this study were Assemblage AI and E. The results indicated that dairy cattle may act as a potential risk of Giardia transmission among animals and humans (especially Assemblage AI).

Humoral immune response of dairy cattle immunized with rBm95 (KU-VAC1) derived from Thai Rhipicephalus microplus.

Rhipicephalus (Boophilus) microplus is an important cause of economic losses in Thailand through direct effects of feeding on cattle and pathogen transmission. Current tick control methods rely on expensive chemical acaricides that result in environmental contamination, residues in food animal products and acaricide-resistant ticks. Anti-tick vaccines based on concealed antigens have shown promising results in the control of cattle tick. Thus, recombinant Bm95 (rBm95) from Thai R. microplus (KU-VAC1) was cloned and expressed to test as an anti-tick vaccine in Thailand. The objective of this study was to compare antibody responses induced by KU-VAC1 to that obtained after vaccination with Gavac that is based on the Bm86 homologue. Four groups of six cattle each were immunized with KU-VAC1, Gavac, adjuvant or phosphate-buffered saline, and boosted three times at 21-day intervals. Enzyme-linked-immunosorbent serologic assay were used to measure the humoral antibody responses specific to Thai rBm95. Cattle immunized with either KU-VAC1 or Gavac showed significantly greater antibody production than the controls. Antibody titres were detected after the first immunization and peaked after the seventh week. These results indicated that KU-VAC1 and Gavac are similarly immunogenic, and that further studies are warranted to compare performance parameters of ticks fed on immunized cattle.

Prevalence and molecular characterization of bovine Cryptosporidium from dairy cows in Northern Thailand

Cryptosporidiosis is a common protozoan infection in humans and domestic animals. It is the culprit for significant neonatal morbidity in cattle as well as weight loss and delayed growth, which leads to large economic losses in the farming industry. Furthermore, bovine Cryptosporidium is also a principal source of human Cryptosporidium infections. The purpose of this study is to determine prevalence and genotype of Cryptosporidium spp. from feces of dairy cows from the northern parts of Thailand (Chiang Rai, Chiang Mai, and Lumpang provinces). A total of 500 fecal samples were collected directly from the rectum and they were examined for potential presence of Cryptosporidium infection by using tests such as DMSO-modified acid fast stain, immunofluorescence antibody test (IFAT) and polymerase chain reaction (PCR). The prevalence of Cryptosporidium spp. was 5% by DMSO-modified acid fast stain, 7% by IFAT and 7.6% by PCR respectively. The main genotypes of Cryptosporidium spp. identified were Cryptosporidium parvum and Cryptosporidium bovis. Therefore, as a result of this study, it can be said that, due to the potential cross-species transmission of Cryptosporidium parvum, infected dairy cows may pose a potential zoonotic risk to humans.