Effects of feeding pasteurized waste milk or saleable milk to calves on weight, health and fecal Escherichia coli antimicrobial resistance.

The aim of this study was to compare the effects of feeding pasteurized waste milk or saleable milk to calves on weight, health and emergence of antimicrobial resistance in Escherichia coli strains isolated from those calves. An experimental study under field conditions on a commercial pasture-based Argentinian dairy farm was carried out. Forty Holstein calves were assigned randomly to either pasteurized waste milk (PWM) or non-pasteurized saleable milk (SM). The antimicrobial agents (AM) used on the farm, both to treat or prevent diseases, were recorded. The passive immunity level, calf live weight, AM presence in milk, clinical examination of calves, and E. coli isolation and identification, were performed. A total of 258 E. coli strains were isolated from fecal samples (132 isolates from SM calves and 126 from PWM calves at six sampling times). All E. coli isolated were used to perform AM susceptibility tests (disc diffusion and agar dilution). No differences were observed between groups in health parameters, average daily gain or prevalence of resistant E. coli strains to any AM evaluated throughout the study. Peaks of trimethoprim, sulfamethoxazole and enrofloxacin minimum inhibitory concentration (MIC) were observed at 30 d in E. coli from both groups of calves, whilst additional peaks to tetracyclin and ampicillin were observed only in SM calves. All MIC apart from gentamicin decreased at 75 and 90 d of age (during the weaning period). Gentamicin MIC behaved differently, having no peaks and increasing at 90 d only in PWM group. In conclusion, we found no evidence that emergence of antibiotic resistance is related to the consumption of pasteurized waste milk.

Short communication: Varroa destructor re-invasion dynamics during autumn and winter in Apis mellifera colonies from a temperate climate.

Infestation with Varroa destructor compromises the survival of Apis mellifera colonies, especially during the winter season. In order to prevent colony losses due to the presence of Varroa mites, determination of the infestation level and the application of autumn treatment is highly recommended. However, autumn reinvasion by inter-apiary and intra-apiary horizontal transmission might threaten the control strategies. Drivers like the infestation level of untreated colonies, the presence of bee brood during late autumn and the colonies disposition within the apiary might explain at least partially the re-invasion rates of treated colonies during autumn and winter. A total of six apiaries with five colonies were distributed within a 30 km radius. Colonies were arranged within each apiary following a circular or a lineal disposition. Twenty-four of the thirty colonies were treated during late summer against V. destructor and one colony per apiary remained untreated. The phoretic Varroa infestation and the adult bee population, brood area and nutritional reserves in the colonies was estimated before and after treatment and then for the next four months (late autumn and winter season). In this study, a model for the V. destructor re-invasion dynamics during autumn and winter in honey bee colonies from a temperate climate was fitted. According to these results, the re-invasion probability is higher for lineal disposition of the colonies that also present a higher amount of brood availability during late autumn and winter. Beekeeping practical implications are discussed in the context of an Integrated Pest management approach.

Improvement of bovine pestiviral diagnosis by the development of a cost-effective method for detecting viral RNA in fresh specimens and samples spotted in filter papers.

Bovine pestiviruses are the causative agents of bovine viral diarrhea, a disease that causes severe economic losses in cattle. The aim of this study was to improve their diagnosis by developing a RT-qPCR to detect bovine pestiviruses A, B and H; and to set up a protocol for collecting, shipping and preserving bovine pestiviral RNA on filter papers. The developed RT-qPCR showed high sensitivity in detecting these viruses in different matrices: viral stocks, semen and serum samples. With regard to the possibility of using the technique to test serum pools, it was possible to identify a positive serum sample within a pool containing 30 sera. In addition to evaluating the qPCR from fresh samples, the use of filter papers to sow bovine samples was analyzed. The sampling method on two different filter papers using bovine blood drops was a useful alternative for diagnostic purposes and allowed to preserve pestiviral RNA for up to 12 months under refrigeration.

[Prevalence and geographical distribution of bovine sexually transmitted diseases in the province of Formosa, Argentina]. / Prevalencia y distribución geográfica de las enfermedades de transmisión sexual de los bovinos en la provincia de Formosa, Argentina.

Bovine genital campylobacteriosis (BGC) and bovine trichomonosis (BT) are sexually transmitted diseases (STDs) that affect bovine breeding herds, decreasing their reproductive efficiency. The objective of this work was to estimate the prevalence of these diseases and their temporal-spatial distribution in the province of Formosa, Argentina. The cross-sectional study conducted between 2018 and 2021 included a total of 15,571 bulls, inter-herd prevalence being 29.62% and 17.23% for BGC and BT, respectively. The prevalence of positive animals was 2.05% for BGC and 0.43% for BT. The temporal-spatial analysis of BGC showed two distinct spatial groupings, one group had a low risk of contracting the disease (RR = 0.13; p < 0.001; 2018-2021) while the other group had a high risk (RR = 2.84; p < 0.001; 2020-2021). BT had a high-risk group for the disease (RR = 35.24; p < 0.001; 2019). This study shows that STDs are endemic in the region, providing updated and valuable information as a tool for the health management of these diseases.

Field evaluation of Varroa-resistance traits in surviving Apis mellifera colonies in Argentina.

Varroa destructor is one of the most important sanitary threats for the beekeeping industry and so far disease control is based mainly on chemical treatment. However, a long-term solution may arise from studying natural surviving colonies of Apis mellifera. We compared the Varroa infestation rate in six commercial colonies that received annual treatment against mites and six non-treated colonies that survived in absence of any treatment for the last 6 years. In addition, we evaluated two potential mechanisms that might be involved in colony survival: hygienic (HYG) and Varroa-sensitive hygiene behavior (VSH) by means of pin-killed and mite artificial infestation, respectively. HYG and VSH were negatively correlated with mite infestation independently of the colony group (treated or non-treated). Furthermore, colonies expressing high levels of pupae removal (≥ 80%) showed higher %HYG and lower mite infestation compared to colonies showing low pupae removal (< 80%). The analysis of reproductive status of mites from the non-removed infested cells evidenced that more infertile mites are found in colonies with more than 80% of pupae removal. To study non-treated colonies that survive for several years, it is a suitable approach for identifying the underlying mechanisms related to Varroa-resistance.

Efficacy of Panax ginseng extract combined with cephalexin as a dry cow therapy.

Our objective was to evaluate the efficacy of intramammary administration, at drying-off, of a Panax ginseng extract (PGe) combined with cephalexin (Ceph) on the post-calving bacteriological cure rate of pre-existing intramammary infections (IMI) and on the occurrence of new IMI during the dry period. In addition, milk yield and somatic cell count (SCC) in the post-treatment lactation were evaluated. One hundred and eight late-lactation cows were randomly divided into two experimental groups and were treated at drying-off with Ceph alone or PGe combined with Ceph.Cure rates for IMI present at drying-off were similar for both treatments (OR = 0.95, 95% CI = 0.33-2.74). Cure rates for Staphylococcus aureus were lower (OR = 15.4, 95% CI = 1.66-142.52) in quarters treated with PGe + Ceph than in those treated with Ceph alone. Intramammary infusion of PGe + Ceph at drying-off had no effect on preventing new dry period IMI (OR = 0.75, 95% CI = 0.38-1.51), compared with infusion of Ceph alone. Milk production and SCC in the ensuing lactation were not affected by PGe + Ceph treatment. In conclusion, addition of PGe to dry cow therapy did not show any advantage over the use of dry cow therapy alone.

Risk factors of S. aureus intramammary infection in pre partum dairy heifers under grazing conditions and molecular characterization of isolates from heifers and cows.

The aims of the research reported here were to identify potential risk factors associated with the presence of Staphylococcus aureus intramammary infection (IMI) in pre partum dairy heifers on 17 dairy farms from three provinces of Argentina and to characterize, at molecular level, isolates from those heifers and lactating cows from two selected herds. A total of 1474 heifers and 4878 lactating cows were studied. The prevalence of Staphylococcus aureus IMI in the heifers, heifers at quarter level and lactating cow mammary quarters was 14.41, 4.82, and 14.65%, respectively. Univariate analysis showed the key variables associated with S. aureus IMI presence in the heifers were: S. aureus IMI prevalence in cows of the lactating herd, the time calves stayed with their dam after birth, the calf rearing system, the place of rearing (own farm or other dairy farm) and fly control on the farm. None of the variables included in the multivariable analysis was associated with the presence of S. aureus IMI in the pre partum heifers, probably due to low variability among management practices used by the farms for rearing the heifer calves. At the molecular level, S. aureus isolates were grouped into three main PFGE clusters and several genotypes within the clusters. Isolates from mammary secretion of pre partum heifers and milk of lactating cows comprised different PFGE clusters in both herds, although two exceptions occurred. The absence of gene fnbpB, which codifies for a virulence factor protein involved in cell invasion by S. aureus, was significantly more frequent in pre partum heifer secretion isolates than in isolates from lactating cow milk. These results suggest that, under these management conditions, isolates from mammary secretions of pre partum heifers do not originate from the milk of lactating cows, but rather other sources to which the heifer is exposed.

Prevalence of honey bee (Apis mellifera) viruses in temperate and subtropical regions from Argentina.

In Argentina, bee virus studies are still incipient, and there are no studies regarding the climatic effect. The aim of this study was to assess and compare the presence of honeybee viruses in different climatic regions from Argentina. A total of 385 colonies distributed in five Argentinean eco-regions were examined to evaluate the percentage of infestation with Varroa destructor and the presence of seven virus species (Deformed wing virus, DWV; Acute bee paralysis virus, ABPV; Chronic bee paralysis virus, CBPV; Black queen cell virus, BQCV; Kashmer bee virus, KBV; Israeli acute bee paralysis virus, IAPV; and Sacbrood bee virus, SBV) after honey yield. Two viruses, KBV and IAPV, were not detected. The other five viruses were found in different prevalences: DWV (35%), ABPV (21.5%), BQCV (8.0%), CBPV (2.2%), and SBV (1.1%). We found double and triple viral associations in approximately 25% of the sampled colonies. The mean V. destructor infestation in the colonies prior to the acaricide treatment was 7.12%±8.7%. The knowledge of the prevalence of these viruses in the region and their relation with the mite and other possible influencing factors is important for preventing colony losses. Further studies are necessary to identify the risk factors associated with virus presence and its relationship with other pathogens such as V. destructor.

Distribution and prevalence of Nosema apis and N. ceranae in temperate and subtropical eco-regions of Argentina.

A total of 361 colonies from 59 apiaries located in two temperate and three subtropical eco-regions were examined during the post-harvest period to determine distribution and prevalence of Nosema spp. Apiaries from subtropical eco-regions showed a lower spore count than those from temperate eco-regions. Pure N. ceranae and co-infection were detected in apiaries from all regions. In contrast, pure N. apis infection was exclusively observed in the subtropical study region. The predominant detection of N. apis in a subtropical region joining a southern temperate region where mainly co-infected apiaries were identified is in contrast to previous reports.

[Knowledge of zoonoses transmission routes and of the species concerned among rural workers]. / Conocimiento de las vías de transmisión de las zoonosis y de las especies afectadas entre los trabajadores rurales.

The aim of this study was to evaluate the level of awareness of zoonoses among rural workers and their potential associations with socio-demographic factors. A cross-sectional study was performed by holding personal interviews (N=110, n=94) using a structured questionnaire. The statistical analysis included the χ(2) test, the Student's t test and Pearson and Spearman correlations. The highest level of awareness was found for trichinosis, rabies and scabies. Species transmitting brucellosis, tuberculosis and anthrax were well known, but not their modes of transmission. The least known diseases were toxocariasis and hydatidosis, followed by leptospirosis and toxoplasmosis. Significant associations were found (p<0.001) between the knowledge of transmitting species and the modes of transmission. Senior male owners, married, and living in urban areas showed the highest overall knowledge of zoonoses. Awareness of zoonoses among rural workers is inadequate. Veterinarians in conjunction with risk insurers may play a key role in providing information to people at risk.

First large-scale study reveals important losses of managed honey bee and stingless bee colonies in Latin America.

Over the last quarter century, increasing honey bee colony losses motivated standardized large-scale surveys of managed honey bees (Apis mellifera), particularly in Europe and the United States. Here we present the first large-scale standardized survey of colony losses of managed honey bees and stingless bees across Latin America. Overall, 1736 beekeepers and 165 meliponiculturists participated in the 2-year survey (2016-2017 and 2017-2018). On average, 30.4% of honey bee colonies and 39.6% of stingless bee colonies were lost per year across the region. Summer losses were higher than winter losses in stingless bees (30.9% and 22.2%, respectively) but not in honey bees (18.8% and 20.6%, respectively). Colony loss increased with operation size during the summer in both honey bees and stingless bees and decreased with operation size during the winter in stingless bees. Furthermore, losses differed significantly between countries and across years for both beekeepers and meliponiculturists. Overall, winter losses of honey bee colonies in Latin America (20.6%) position this region between Europe (12.5%) and the United States (40.4%). These results highlight the magnitude of bee colony losses occurring in the region and suggest difficulties in maintaining overall colony health and economic survival for beekeepers and meliponiculturists.

Zoonoses in rural veterinarians in the central region of Argentina.

OBJECTIVE: To estimate the frequency of zoonoses in rural veterinarians and to search for risk factors. DESIGN: Cross-sectional study based on an anonymously answered structured questionnaire. SETTING: The interviewees participated in mandatory continuing education classes scheduled throughout the province by the College of Veterinary Surgeons. PARTICIPANTS: Overall, 741 professionals were surveyed, and 75.8% (n = 562) of them completed the structured questionnaire. MAIN OUTCOME MEASURES: Cumulative incidence (CIR) and incidence density (IDR) rates, standardised rates, χ(2) , Student's t-test, Pearson's correlation coefficient and logistic regression. RESULTS: The CIR for all zoonoses was 34.1% (brucellosis, 29.1%; toxoplasmosis, 2.1%; leptospirosis, 0.6%; tuberculosis, 0.6%; anthrax, 0.6%; ringworm, 0.4%; other, 0.6%). The IDR for the period 1964-2008 was estimated to be 20.7% (19.5% for brucellosis). The brucellosis IDR decreased between 1964 and 2008 and was higher during early post-graduation. The risk of brucellosis was associated with the number of years of practice and the geographical area. Sixty-nine respondents had at least one day of absence from work (24.0 ± 27.8 days). CONCLUSIONS: A high frequency of zoonoses was reported by veterinarians with a large animal practice. Although the rate of zoonoses may be decreasing, further studies are needed to confirm this finding. A joint effort of all institutions is needed to prevent zoonoses among private practitioners.

Antibodies to SARS-CoV2 induced by vaccination and infection correlate with protection against the infection.

The COVID-19 pandemic remained worldwide for almost three years, but little is known about the dynamics of humoral immune response to the third dose over time and its protection from infection. Our aim was to assess the humoral immune response after the third dose of the different vaccines administered to SARS-CoV-2 naive and previously infected individuals, and its correlation with protection in an academic community. For each person studied (185), three blood samples were taken between December 2021 and July 2022, one month apart. Anti-S antibodies were quantified by ELISA, while anti-N antibody levels were determined by ECLIA. Most of the participants had received two doses of viral vector-based, mRNA-based and virus-inactivated vaccines. Although anti-N antibody levels revealed that 80% of the individuals had been exposed to the virus before or during the study, only 42% reported having been diagnosed. When anti-S IgG levels were measured 3-5 months after the second dose of any vaccine, they were higher in those previously infected individuals. The same results were observed for anti-N IgG levels in those who received 2 doses of the virus-inactivated vaccine. When analyzing the dynamics of anti-S antibodies we observed that, although positive IgG antibody levels were detected 5-6 months after the second dose administration, those observed 30-60 days after the third dose were significantly higher and remained so for at least 8 months. Higher levels of anti-S IgG antibodies at the first sampling were associated with a lower incidence of subsequent infection. The same association was seen in people who received the booster compared with those who received two doses. This study provides further evidence that anti-S IgG antibodies remained at high levels over time, and both anti-S levels and the third dose of anti-SARS-CoV-2 vaccine correlate with protection against the infection. It also shows that infection acts as a booster of immunization, increasing levels of both anti-N and anti-S IgG.

Evaluation of frequency of antibodies against Neospora caninum, Toxoplasma gondii and Brucella melitensis, risk factors and spatial distribution of infection in goat and sheep flocks from Argentina.

Neospora caninum, Toxoplasma gondii and Brucella melitensis are pathogens that cause abortion in small ruminants. Besides, B. melitensis and T. gondii are zoonotic pathogens. The aim of this study was to describe the frequency of antibodies against N. caninum, T. gondii and B. melitensis in sheep and goats from three provinces of the center region of Argentina. In addition, the spatial distribution of the infected flocks/herds and risk factors were evaluated. A cross-sectional study was conducted from 2015 through 2016. Serum samples from 4783 goats and 1524 sheep from 186 goat, 51 sheep and 38 mixed flocks/herds were analyzed. Competitive inhibition enzyme-linked immunosorbent assay (ciELISA) and indirect fluorescent antibody test (IFAT) were performed for detection of antibodies against N. caninum and IFAT for T. gondii. The buffered plate antigen test and complement fixation test were performed for detection of antibodies against B. melitensis. The frequency of anti-T. gondii antibodies was 41.2% and 29.7% for sheep and goats, respectively. The frequency of anti-N. caninum antibodies was 17.2% and 14% for sheep and goats, respectively. About 97.1% of the sheep flocks, 79.4% of the goat herds and the 91.3% of the mixed flocks had seropositive animals to T. gondii. About 61.8% of the sheep flocks, 58% of the goat herds and the 82.6% of the mixed flocks had seropositive animals to N. caninum. All the analyzed animals were negative to anti-B. melitensis antibodies. For T. gondii, a significant cluster of high risk of seropositive flocks/herds was detected in the littoral of the Parana River. The province of origin of the flock/herd was the only variable associated to T. gondii positivity (p = 0.003). Animals from Santiago del Estero and Santa Fe Provinces had 3.48 and 1.77 times more risk to be positive to T. gondii than animals from Entre Ríos Province, respectively. For N. caninum, a cluster of high risk of seropositive flocks/herds was detected in the north of Santa Fe Province. The only explanatory variable associated to N. caninum positivity was animal species (p = 0.003). Sheep had 1.73 times more risk to be positive to N. caninum than goats. The absence of antibodies against B. melitensis in all the analyzed animals is an important finding for the public health of the region. Since bordering provinces have infected flocks/herds, brucellosis in small ruminants should be under epidemiologic surveillance in the region.

Seroprevalence and risk factors associated with bovine Leukemia virus infection in argentine beef cattle.

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis, an endemic disease in dairy cattle of Argentina. However, little is known about the seroprevalence of BLV in beef cattle. In this study, we conducted a cross-sectional study including farms from thirteen provinces of Argentina. A total of 5827 bovine serum samples were collected from 76 farms and analyzed using an in-house developed enzyme-linked immunosorbent assay. Information about herd management was collected through a questionnaire, and univariate and multivariate analyses were performed to detect risk factors associated with BLV infection. Herd-level seroprevalence was 71.05%, while the mean animal-level seroprevalence was 7.23% (median = 2.69%; min = 0, max = 75). Only two provinces had no positive BLV samples. The other eleven provinces showed more than 50% of their farms infected with BLV. The multivariate model revealed that BLV prevalence was significantly associated with the use of animals raised in the same farm for cattle replacement (P = 0.005), breeding cows by natural mating with a bull (P < 0.001), and weaning calves after 6 months of age (P = 0.011). This extensive study revealed that BLV seroprevalence in Argentine beef farms has increased during the last years and allowed identifying some management practices associated with BLV prevalence. These data deserve special attention because BLV infection in beef cattle seems to lead to a dissemination pattern similar to that observed during the last decades in dairy cattle, especially considering that Argentina is the sixth beef producer in the world, with about 5% of global beef production.

Antimicrobial resistance of Streptococcus uberis isolated from bovine mastitis: Systematic review and meta-analysis.

Streptococcus uberis is one of the most common pathogens associated with bovine mastitis, commonly treated with antimicrobials (AM), favoring the appearance of antimicrobial resistance (AMR). The objective of this work was to determine the proportion of phenotypic AMR among S. uberis isolated worldwide from bovine intramammary infections between the years 1983-2022, and to assess the variables associated by means of a systematic review and metanalysis. Sixty articles were eligible for quantitative review. Ninety-four independent studies were obtained. The antimicrobials evaluated in more S. uberis strains were penicillin (21,987 strains), oxacillin (21,727 strains), erythromycin (20,013 strains), and ampicillin (19,354 strains). Most of the studies included in this meta-analysis were from Europe (44), followed by America (25), Africa (10), Asia (10), and Oceania (5). Among the included articles, 22 were published from 1983 to 2006, 23 from 2007 to 2012, 25 from 2013 to 2015, and the remaining 24 after 2016. Penicillin, erythromycin, and tetracycline were the antimicrobials with >25 studies. Therefore, the following analyses were performed only for these antimicrobials, presenting a high heterogeneity index (I2). The variability observed for penicillin and tetracycline was only explained, partially, by continent of origin. The variability observed for erythromycin was not explained by any of the potential explanatory variables included in this study. The S. uberis proportion of resistance to antimicrobials is highly variable and probably influenced by many factors other than those studied in this meta-analysis, where it was not possible to inform a unique average proportion of resistance.

Association between milking practices and psychrotrophic bacterial counts in bulk tank milk.

The objective of this work was to determine on-farm risk factors for psychrotrophic bacterial counts in bulk tank milk from dairy farms in Argentina. Raw milk samples from bulk tanks of 27 dairy farms were examined for total psychrotrophic counts (TPC), proteolytic psychrotrophic counts (PPC) and lipolytic psychrotrophic counts (LPC) (dependent or outcome variables). A survey recording infrastructure conditions, milking equipment and milking management (independent variables) was performed. Bivariate association proofs and logistic regression analyses were used to determine association between independent variables and psychrotrophic bacterial counts. Milk cooled in plate heat exchangers or barrel tanks were 16.39 and 10.52 times more likely to yield TPC and PPC above the standard established for high quality milk compared with milk cooled in bulk tanks, respectively. Periodic cleaning of cooling tanks (3 times a week or daily) was associated with lower TPC (approximately 1.5 log CFU/ml) than weekly cleaning frequency and farms where milkers did not wash their hands during milking time were 7.81 times more likely to have higher PPC. No association was found between LPC and any of the independent variables. The only variable associated with TPC and PPC in a logistic regression model was the refrigeration system used on the farm. Dairy farms that possessed bulk milk cooling tanks yielded the lowest bacterial counts. Results of this study highlight the importance of both the type of cooling system used on the farm and its adequate hygienic maintenance for obtaining low pshychrotrophic counts at dairy farm.

Antimicrobial resistance of Staphylococcus aureus isolated from bovine mastitis: Systematic review and meta-analysis.

Staphylococcus aureus, one of the main contagious mastitis pathogens worldwide, is characterized for causing chronic intramammary infections that respond poorly to antimicrobial therapy, disseminating within the herd leading to high economic losses. The aim of this study was to determine the prevalence of phenotypic resistance to antimicrobial agents among S. aureus collected worldwide in the context of bovine intramammary infections between the years 1969-2020. A systematic review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). One hundred and fifty-five articles were eligible for quantitative review. Most of studies included in this meta-analysis were from Europe (88), followed by Asia (56), Latin America (39), Africa (32), North America (26), and Oceania (8). The highest overall prevalence of resistant S. aureus was against penicillin (pestimate 0.451, CI95 % 0.415-0.487), followed by clindamycin, erythromycin, and gentamycin (p-estimate = 0.149, 0.085, and 0.069, respectively). Ceftiofur and cephalotin presented the lowest overall prevalence of antimicrobial resistance (AMR, p-estimate = 0.020 and 0.015, respectively). The AMR to almost all the antimicrobials evaluated presented an increasing pattern over time, more apparent from 2009 onwards. The antimicrobials with a higher increase in their AMR prevalence over time were clindamycin, gentamycin, and oxacillin. Africa, Asia and Latin America were the continents with higher AMR to most compounds included in this study. No differences in AMR were detected regarding the clinical origin of the isolates (subclinical vs clinical mastitis) for almost all antibiotics evaluated. Differences in the method for testing AMR (disc diffusion method vs minimum inhibitory concentration) and type of study design for monitoring AMR were detected underscoring the importance of these variables as critical factors to enable comparisons for evaluating emergence of AMR.