Epidemiology of Neospora caninum infection in dairy cattle in Thailand

The protozoan parasite Neospora caninum is causing bovine abortion worldwide. The overall aim of this thesis was to gain a better understanding about N. caninum infection in dairy cattle in Thailand both at the individual animal and the herd level. Specifically, the aims were to investigate variations of N. caninum antibodies in milk of individual cows during lactation, to demonstrate the use of bulk milk antibody testing and its application, and to characterize N. caninum dynamics of infection in Thai dairy herds. The thesis is based on four separate studies. The levels of N. caninum antibodies in milk of 15 infected cows varied considerably during 18 months although they were consistently considered positive. Cows of all lactation groups had a higher milk antibody at calving compared to at later months after calving, but the only significant difference was in the first lactation. Serum and milk antibody levels were always lower in first lactation than in second and later lactations. The results showed that individual milk can be an alternative material to demonstrate presence of N. caninum antibodies in lactating cows. The bulk milk antibody levels in a cross-sectional sample of 11 herds ranged between 0.04 and 0.89 and the seroprevalences varied between 0% and 46%. Herds with higher bulk milk antibody levels showed a trend of higher portion of seropositive cows although there was no strong relationship between the bulk milk antibody level and the within-herd seroprevalence. Forty-six percent of the 220 bulk milk samples from nine milk collection centres were judged positive and the herd prevalence varied between milk collection centres. Repeated bulk milk antibody testing of 418 dairy herds was evaluated and the herd N. caninum status was established at three consecutive samplings during one year. Herd status at either of the first two samplings was used to predict herd status at the last sampling, and was also interpreted in combinations. Using combinations gave higher predictability of a herd’s Neospora status than a single test. One hundred and thirty-six were considered negative, and one hundred and thirty-four herds were positive throughout the study. It was concluded that repeated bulk milk testing at regular intervals provided better information about herd N. caninum-antibody status than a single test. The results also showed that the infection is prevalent in northeast Thailand, but that a herd can keep a negative infection status. When 11 dairy herds were investigated repeatedly during four years, the overall percentage of antibody-positive cattle was constant and varied only between 10% and 13%. However, the within-herd seroprevalence differed substantially between herds. Vertical transmission, i.e. from dam to calf, was the most frequent route of transmission. The proportions of individual animals that changed from being seronegative to seropositive and from being seropositive to seronegative between the years were 3.9-4.6% and 19-39%, respectively, although most animals had consistent serological status throughout the study. Some herds can thus keep free from N. caninum infection without farmers taking control measures

EFFICACY OF GUAVA LEAF EXTRACT AS ALTERNATIVE PRE-MILKING TEAT DIPPING IN REDUCING TEAT–END BACTERIAL LOAD OF MILKING DAIRY COWS

Objective: To investigate the efficacy of aqueous methanolic guava leaf extracts used as pre-milking teat disinfectant on teat-end bacterial load reduction in lactating dairy cows.Methods: Two test-skin swabs of before and after teat dipping with 50% aqueous methanolic guava leaf extract were evaluated for the bacterial loads, i.e. total bacterial count (TBC), staphylococcal count (STA), streptococcal count (STR) and coliform count (COL), using 16 lactating cows on a smallholder dairy farm in Khon Kaen, Thailand. Commercially available common chemical disinfectants were also comparatively investigated.Results: Guava leaf extracts and the two others dis infectants showed reduction of the teat-end TBC and STA significantly while there was the decrease in teat-end STR and COL but the result was not significant in statistical analysis. Overall, applying the pre-milking teat dipping showed significant reduction of teat-end bacterial loads when compared to routine udder sanitization without teat dipping.Conclusion: The guava leaf extract can be used as an alternative of pre-milking teat disinfectant for reducing the teat-end bacterial loads. This may lead to lower chemical uses, which may promote more hygienic, safe milk for consumers, and decrease costs of mastitis risk control, especially in the developing and the third world countries where guava is native and easy to obtain.Â

Global distribution of Bartonella infections in domestic bovine and characterization of Bartonella bovis strains using multi-locus sequence typing

Bartonella bovis is commonly detected in cattle. One B. bovis strain was recently isolated from a cow with endocarditis in the USA, suggesting its role as an animal pathogen. In the present study, we investigated bartonella infections in 893 cattle from five countries (Kenya, Thailand, Japan, Georgia, and Guatemala) and 103 water buffaloes from Thailand to compare the prevalence of the infection among different regions and different bovid hosts. We developed a multi-locus sequence typing (MLST) scheme based on nine loci (16S rRNA, gltA, ftsZ, groEL, nuoG, ribC, rpoB, ssrA, and ITS) to compare genetic divergence of B. bovis strains, including 26 representatives from the present study and two previously described reference strains (one from French cows and another from a cow with endocarditis in the USA). Bartonella bacteria were cultured in 6.8% (7/103) of water buffaloes from Thailand; all were B. bovis. The prevalence of bartonella infections in cattle varied tremendously across the investigated regions. In Japan, Kenya, and the Mestia district of Georgia, cattle were free from the infection; in Thailand, Guatemala, and the Dusheti and Marneuli districts of Georgia, cattle were infected with prevalences of 10–90%. The Bartonella isolates from cattle belonged to three species: B. bovis (n=165), B. chomelii (n=9), and B. schoenbuchensis (n=1), with the latter two species found in Georgia only. MLST analysis suggested genetic variations among the 28 analyzed B. bovis strains, which fall into 3 lineages (I, II, and III). Lineages I and II were found in cattle while lineage III was restricted to water buffaloes. The majority of strains (17/28), together with the strain causing endocarditis in a cow in the USA, belonged to lineage I. Further investigations are needed to determine whether B. bovis causes disease in bovids.Specimens from cattle in Kenya were collected under a project supported by the Wellcome Trust, UK (grant number 081828/B/06/Z).http://www.plosone.orgam2014ab201

BVDV and BHV-1 Infections in Dairy Herds in Northern and Northeastern Thailand

Bulk milk samples from 220 dairy herds were collected at 9 public milk collection centres in the northeastern and northern Thailand, and a subset of 11 herds was selected for individual testing. The samples were tested for presence of antibodies to BVDV and BHV-1 using an indirect ELISA. The results from the bulk milk testing demonstrated a moderate level of exposure to BVDV and BHV-1 (73% and 67%, respectively). However, the low proportion of herds with high BVDV antibody-levels (13%) and the low within-herd seroprevalence of BVDV and BHV-1 in the 11 herds (24% and 5%, respectively), particularly among the young stock (15% and 0%, respectively), demonstrated a low prevalence of active BVDV infection and a low rate of reactivation of latent BHV-1. The presence of a self-clearance process was also indicated by the results from the individual testing. Moreover, a surprisingly low prevalence of BVDV and BHV-1 antibody-positive herds at one of the milk centres was found. This centre was established 5–10 years before the others. Our impression is that this reflects the self-clearance process, where consecutive replacement of imported infected animals without further spread has resulted in a nearly total elimination of the infections. Based on our experiences and on these results we are convinced that this process can continue if there is awareness of herd biosecurity. This is especially important in the context of a future intensification of the dairy production

Evaluation of Immunodiagnostic Performances of <i>Neospora caninum</i> Peroxiredoxin 2 (NcPrx2), Microneme 4 (NcMIC4), and Surface Antigen 1 (NcSAG1) Recombinant Proteins for Bovine Neosporosis

Bovine neosporosis is among the main causes of abortion in cattle worldwide, causing serious economic losses in the beef and dairy industries. A highly sensitive and specific diagnostic method for the assessment of the epidemiology of the disease, as well as it surveillance and management, is imperative, due to the absence of an effective treatment or vaccine against neosporosis. In the present study, the immunodiagnostic performance of Neospora caninum peroxiredoxin 2 (NcPrx2), microneme 4 (NcMIC4), and surface antigen 1 (NcSAG1) to detect IgG antibodies against N. caninum in cattle were evaluated and compared with that of the indirect fluorescent antibody test (IFAT). The results revealed that NcSAG1 had the highest sensitivity and specificity, with values of 88.4% and 80.7%, respectively, followed by NcPrx2, with a high sensitivity of 87.0% but a low specificity of 67.0%, whereas NcMIC4 showed sensitivity and specificity of 84.1% and 78.9%, respectively, when compared with IFAT. A high degree of agreement was observed for NcSAG1 (k = 0.713) recombinant protein, showing the highest diagnostic capability, followed by NcMIC4 (k = 0.64) and NcPrx2 (k = 0.558). The present study demonstrates that NcSAG1 is helpful as an antigen marker and also demonstrates the potential immunodiagnostic capabilities of NcPrx2 and NcMIC4, which could serve as alternative diagnostic markers for detecting N. caninum infection in cattle. These markers may find utility in future treatment management, surveillance, and risk assessment of neosporosis in livestock or other animal host species. Further research should be directed toward understanding the in vivo immune response differences resulting from immunization with both recombinant proteins

Phylogenetic relationships of the 28 <i>B. bovis</i> isolates inferred from 5085bp - 5119bp concatenated sequences of <i>ftsZ</i>, <i>gltA</i>, groEL, <i>nuoG</i>, <i>ribC</i>, <i>rpoB</i>, <i>ssrA</i>, and ITS fragments.

<p>Following each isolate are geographical origin, bovine host source, and sequence type (ST) classification. Phylogenetic tree was constructed by N-J method, and bootstrap values were calculated with 1,000 replicates. A total of 22 STs were identified, which fall into three lineages (square circled clades). </p