No abstract

Equine herpesvirus 1 (EHV-1) is the causative agent of abortion, perinatal foal mortality, neurological and acute respiratory diseases in horses. Conventional laboratory diagnosis involving viral isolation from aborted foetuses is laborious and lengthy and requires processing of samples within 24 h of collection, which is problematic for samples that come from long distances. The aim of this study was to develop a polymerase chain reaction (PCR) assay useful in Argentina to detect DNA sequences of EHV-1 in different tissues from aborted equine foetuses with variable quality of preservation and without the use of conventional DNA fenolic extraction. Several DNA extraction protocols and primers were evaluated. The amplification method was standardized and its specificity was analysed using 38 foetal samples of variable quality of preservation. Of the 38 different foetal tissues, nine livers, six spleens and two lungs in good preservation and eight livers, one spleen and four lungs in a poor state of preservation were positive for PCR. EHV-1 was recovered only from the nine livers, five spleens and two lungs in good preservation. No virus was isolated from the samples that were poorly preserved. Viral isolation was confirmed by cytopathic effect and indirect immunofluorescence. The specificity of the PCR results was confirmed by the restriction endonuclease digestion of PCR products and hybridization.

The objective of the present study was to assess the relationship between individual cow milk yield and fertility, accounting for the contextual effect of the herd. A data set including 657,968 lactations from 677 dairy herds in Argentina from 2001 to 2012 was used. The odds of pregnancy by 100 d in milk (DIM) were assessed by a multilevel logistic model (with cow as the first and herd as the second hierarchical level), and time to pregnancy was assessed by a proportional hazards regression model. Multilevel logistic models included the fixed effects of milk yield by 80 DIM, parity, year, and calving season at cow level and quartiles of herd milk yield by 80 DIM as a contextual effect. The proportional hazards model included the effect of daily cow-level milk yield as time-dependent variable, with milk yield at herd level as the stratification variable. Cows producing 1 standard deviation over the mean milk yield of their herd had 1.3 percentage point lower pregnancy by 100 DIM (from 31.4 to 30.1%; odds ratio = 0.942) when in herds in the top quartile of milk yield, whereas they increased 0.5 percentage points (from 27.9 to 28.4%) when in herds in the lowest quartile of milk yield. Only 4% of the observed variation in pregnancy by 100 DIM was explained by the random effect of the herd. Similarly, cows producing 1 standard deviation (8 kg/d) greater than the herd mean daily milk had 1.3% lower hazard of pregnancy (hazard ratio = 0.987) at 63 DIM in herds in the top quartile of milk yield, whereas they had 14.8% higher hazard (hazard ratio = 1.148) in herds in the lowest quartile of milk yield. The magnitude of the negative association between the cow's daily milk yield and the hazard of pregnancy increased with DIM. In conclusion, the relationship between milk yield and reproductive performance is statistically significant, but the effect size is practically small and is modulated by herd production level.

Information on reference blood values in the literature is lacking for many wild rodents. In this study, comprehensive reference intervals (RIs) for a wide range of analytes from 101 healthy free-ranging nutria were determined. Animals were captured in Buenos Aires, Argentina (37degrees 50'S, 57 degrees 34'W), and southward (38 degrees 60'S, 58 degrees 23'W), encompassing major biotopes of agricultural pampas with dunes and grassland steppes on the east coast. Traps were set at locations with high-density nutria populations (i.e., those areas that showed signs of movement, territorial marking, or feeding activities). Although the small sample size limits the interpretation of these findings, RIs were determined by a robust method using the central 95th percentile. In nutria, the RI range varied greatly for the leukocyte differentials, with mature neutrophils: 3,907-5,544/mmicrol for females and 3,744-5,900/microl for males; band neutrophils: 0-10/ll for females and 3-18/microl for males; lymphocytes: 4,213 5,940/microl for both sexes combined; monocytes: 165-402/microl for both sexes combined; eosinophils: 13-91/microl for females and 108-165/microl for males; and basophils: 0-87/microl for both sexes combined. Platelet concentration was 543-727 x 10(9)/L for both sexes combined. There was also a wide RI range for biochemistry values for some enzymes, such as alkaline phosphatase: 200-399 IU/L for both sexes combined; cholinesterase: 762-1,407 IU/L for females and 763-1,284 IU/L for males; creatine kinase: 182-552 IU/L for females and 162-451 IU/L for males; amylase: 853-1,865 IU/L for females and 779-1,293 IU/L for males; and glucose concentration 120.2-180.6 mg/dl for both sexes combined. Conversely, there was not a wide pooled RI range for calcium: 7.0-11.2 mg/dl; phosphorous: 6.1-9.3 mg/dl; sodium: 133.0-159.0 mEq/L; potassium: 3.0-8.2 mEq/L; chloride: 101.4-143.0 mEq/L; and urea: 11.3-36.8 mg/dl. The red blood cell indices had a narrow range, with mean corpuscular volume: 84.0 -102.5 fl and mean corpuscular hemoglobin concentration: 18.2-28.8 g/dl, and which was most likely due to strict physiologic controls. The results from this study were similar to those previously reported for farmed nutria.

In this study we developed an indirect ELISA to detect antibodies against Minute Virus of Mice (MVM) using an antigen produced from BHK-21 cells infected with a prototype strain of the virus. The optimal antigen concentration and serum dilutions were established. In order to analyze variability in the laboratory, reproducibility and repeatability within and between plates were determined. Then, a panel of 460 sera from conventional facilities and previously classified as positive or negative by the indirect fluorescent antibody assay was analyzed. The cutoff value was determined by a receiver operating characteristic (ROC) curve. The results of the indirect ELISA were compared with those of the indirect fluorescent antibody assay. The ELISA assay showed 100% sensitivity and 99% specificity. ELISA is a useful tool to be developed in standard virology laboratories and can be used for screening animals faster than the traditional indirect fluorescent antibody assay.