The role of animals as a source of antimicrobial resistant nontyphoidal Salmonella causing invasive and non-invasive human disease in Vietnam.

BACKGROUND: Nontyphoidal Salmonella (NTS) are associated with both diarrhea and bacteremia. Antimicrobial resistance (AMR) is common in NTS in low-middle income countries, but the major source(s) of AMR NTS in humans are not known. Here, we aimed to assess the role of animals as a source of AMR in human NTS infections in Vietnam. We retrospectively combined and analyzed 672 NTS human and animal isolates from four studies in southern Vietnam and compared serovars, sequence types (ST), and AMR profiles. We generated a population structure of circulating organisms and aimed to attribute sources of AMR in NTS causing invasive and noninvasive disease in humans using Bayesian multinomial mixture models. RESULTS: Among 672 NTS isolates, 148 (22%) originated from human blood, 211 (31%) from human stool, and 313 (47%) from animal stool. The distribution of serovars, STs, and AMR profiles differed among sources; serovars Enteritidis, Typhimurium, and Weltevreden were the most common in human blood, human stool, and animals, respectively. We identified an association between the source of NTS and AMR profile; the majority of AMR isolates were isolated from human blood (p < 0.001). Modelling by ST-AMR profile found chickens and pigs were likely the major sources of AMR NTS in human blood and stool, respectively; but unsampled sources were found to be a major contributor. CONCLUSIONS: Antimicrobial use in food animals is hypothesized to play role in the emergence of AMR in human pathogens. Our cross-sectional population-based approach suggests a significant overlap between AMR in NTS in animals and humans, but animal NTS does explain the full extent of AMR in human NTS infections in Vietnam.

Emerging infections: a tribute to the one medicine, one health concept.

Events in the last decade have taught us that we are now, more than ever, vulnerable to fatal zoonotic diseases such as those caused by haemorrhagic fever viruses, influenza, rabies and BSE/vCJD. Future research activities should focus on solutions to these problems arising at the interface between animals and humans. A 4-fold classification of emerging zoonoses was proposed: Type 1: from wild animals to humans (Hanta); Type 1 plus: from wild animals to humans with further human-to-human transmission (AIDS); Type 2: from wild animals to domestic animals to humans (Avian flu) and Type 2 plus: from wild animals to domestic animals to humans, with further human-to-human transmission (Severe Acute Respiratory Syndrome, SARS). The resulting holistic approach to emerging infections links microbiology, veterinary medicine, human medicine, ecology, public health and epidemiology. As emerging 'new' respiratory viruses are identified in many wild and domestic animals, issues of interspecies transmission have become of increasing concern. The development of safe and effective human and veterinary vaccines is a priority. For example, the spread of different influenza viruses has stimulated influenza vaccine development, just as the spread of Ebola and Marburg viruses has led to new approaches to filovirus vaccines. Interdisciplinary collaboration has become essential because of the convergence of human disease, animal disease and a common approach to biosecurity. High containment pathogens pose a significant threat to public health systems, as well as a major research challenge, because of limited experience in case management, lack of appropriate resources in affected areas and a limited number of animal research facilities in developed countries. Animal models that mimic certain diseases are key elements for understanding the underlying mechanisms of disease pathogenesis, as well as for the development and efficacy testing of therapeutics and vaccines. An updated veterinary curriculum is essential to empower future graduates to work in an international environment, applying international standards for disease surveillance, veterinary public health, food safety and animal welfare.

One world--one medicine--one health: emerging veterinary challenges and opportunities.

The interdependence of humans, animals, and their environment has never been more important than now. The most prominent issues putting pressure on global health today include the dramatic emergence and spread of zoonotic diseases, contamination of food, water and soil, bioterrorist events, and degradation of resources and habitats. Current global health challenges have prompted a call for more holistic, collaborative, action-oriented approaches toward the goal of logical and practical solutions. Veterinarians have pivotal obligations, opportunities, and contributions to make in enhancing public health, recognising and responding to zoonotic disease transmission, maintaining food and water quality, and promoting wildlife and ecosystem health.

Antimicrobial resistance in companion animals.

Antimicrobial resistance (AMR) is an emerging problem in companion animals, because of difficult-to-treat infections, possible pressure to use antimicrobials that are important in human medicine, and potential zoonotic transmission. The extent and importance of AMR in companion animals are poorly understood, in part because of limited surveillance; however, it is clear that resistance is problematic in many pathogens and commensals, including staphylococci, enterococci, Escherichia coli and Salmonella.

Potential routes of acquisition of Arcobacter species by piglets.

The aim of this study was to determine the prevalence and the transmission routes of Arcobacter spp. in sows and their offspring on a breeding farm. Twelve Arcobacter-positive sows and their litters were studied for this purpose. Analysis of rectal samples showed a high prevalence of Arcobacter spp. among the sows (approximately 42% of the sows carried one or more Arcobacter species). Intermittent excretion of one particular species and shifts in excretion from one species to another were observed in individual animals over time. The detection of Arcobacter spp. in amniotic fluid of the sows and in rectal samples from newborn piglets (ranging from 38.5-83.3% per litter), as well as the high similarity between PFGE profiles of Arcobacter isolates from sows and their respective newborns indicated the existence of an intra-uterine transmission route for Arcobacter spp. Specific antibodies against Arcobacter spp. were detected in colostrum by Western blot. At 2 weeks of age, only a few piglets were positive for Arcobacter. The reappearance of Arcobacter in these piglets at Week 3 and the shift in the Arcobacter species detected (from a prominent presence of A. cryaerophilus at birth to the presence of A. skirrowii and A. butzleri at 3 weeks after birth) showed that a post-natal infection route from their mothers, newcomers or the environment to the piglets existed. Thus, in this manuscript the transmission of Arcobacter spp. (both vertical and horizontal) from carrying sows to their offspring is demonstrated.

Transmission and control implications of seroconversion to Maedi-Visna virus in Basque dairy-sheep flocks.

A retrospective analysis of seroconversion to Maedi-Visna virus (MVV) was carried out for 10 infected semi-intensively reared dairy-sheep flocks that were tested annually between 1994 and 1999. Four of the flocks raised replacement lambs artificially with bovine colostrum and milk replacement to avoid lactogenic MVV infection but did not prevent aerosol contact between replacements and other sheep in the flock. Flock culling percentages ranged between 14 and 25% and in eight flocks the number of sheep that seroconverted was similar to or lower than the number of sheep culled--suggesting that incidence could be reduced by culling seropositive sheep without increasing average culling percentages. Random-effects logistic regression indicated that seroconversion was associated positively with increasing contact with infected sheep and with lifetime MV-serological status of the dam (used as a proxy measure of genetic susceptibility), but not with mode of rearing pre-weaning (artificially or with a seropositive or seronegative dam). Our results indicate that when conditions allow efficient horizontal transmission, there is no evidence that lactogenic infection increases the risk of MV infection and that there is an important inheritable component of disease resistance or susceptibility.

[Animal feeding and feed legislation after the detection of the first indigenous BSE cases in Germany]. / Tierfütterung und Futtermittelrecht nach den ersten BSE-Nachweisen in Deutschland.

In Great Britain, even the earliest tangible signs indicating the epidemiologic significance of meat and bone meal in the spreading of BSE soon gave rise to increasingly rigorous legislative measures regulating animal feedstuffs. In 1994 a ban on the feeding of animal proteins to ruminants was implemented throughout the entire EU. But until the first BSE cases were actually confirmed in locally raised cattle (November 2000), feeding practice and legislation more or less in Germany remained unaffected by the efforts undertaken in Great Britain. This situation was suddenly changed on 1 December, 2000, when the so-called "Verfütterungsverbot" was put into effect, a law which drastically extended bans regarding the feedstuffs (including fishmeal and animal fats) as well as the species concerned (all animals used in food production). In 2001 the "contamination" phenomenon (ingredients of animal origin were detected in mixed feeds) became a vital issue for the feed industry; through the media, the subject "feedstuff safety" gained a previously unseen level of public awareness. Those circles concerned with mixed feed production and animal husbandry were increasingly confronted with the consequences of the "Verfütterungsverbot" (availability and pricing of substitute ingredients; the demand for amino acids and inorganic sources of phosphorus; problems finding adequate substitutes for animal fats; poor digestibility of alternative components such as indigenous legumes or vegetable fats in calf diets; lower utilization rate of original phosphorus in mixed feeds with negative consequences for skeletal development). With the conditional approval of fishmeal (except in feeds for ruminants) the situation has eased again to a certain degree; on the EU level there are increasing signals pointing toward a political intention to reinstate the utilization of by-products of slaughtered animals qualified for human consumption (with the exception of fallen/dead animals and specific risk material) in poultry and swine feeding. In Germany, at least, the question of animal fat utilization for food-producing animals is still unsolved.

Postweaning multisystemic wasting syndrome induced after experimental inoculation of cesarean-derived, colostrum-deprived piglets with type 2 porcine circovirus.

Cesarean-derived, colostrum-deprived pigs (n = 23) were inoculated intranasally and subcutaneously with a low cell culture passage of type 2 porcine circovirus. In 11 pigs, a persistent fever that lasted 7-17 days began 12-15 days after inoculation with virus. Additional signs of disease in those 11 pigs included depression (11 of 11 pigs), palpable enlargement of inguinal, prefemoral, and popliteal lymph nodes (11 of 11), icterus (6 of 11), and hyperpnea (2 of 11). The remaining 12 pigs had fever that occurred intermittently for 2-4 days between days 12 and 20 postinoculation. Overt signs of disease in those pigs were limited to palpable enlargement of inguinal and popliteal lymph nodes (9 of 12 pigs). When compared with control pigs of similar age, the average daily rate of weight gain for all pigs inoculated with virus was less over a 2-week period that began 2 weeks post inoculation. At postmortem examination, lymph node enlargement was seen in 14 of 14 pigs euthanized between days 20 and 28 postinoculation. Lymph node enlargement was especially prominent in pigs that developed a persistent fever. Microscopic lesions noted in pigs that developed a persistent fever included cellular depletion in lymphoid tissues; hepatic cell necrosis; and lymphogranulomatous inflammation of lymph nodes, Peyer's patches of the intestine, liver, kidney, and heart. Virus was isolated with varying frequency from nasal, rectal, or tonsil swab specimens, buffy coat, serum, urine, and lung lavage fluid obtained antemortem or postmortem. Virus was isolated from or viral DNA was detected in a variety of tissues obtained postmortem up to 125 days postinoculation. Antibody against type 2 porcine circovirus usually was detected in serum between 15 and 20 days postinoculation; however, antibody against virus was not detected in serum from 4 pigs euthanized 20-24 days postinoculation. Direct contact with pigs inoculated with virus 42 days previously resulted in transmission of virus to 3 of 3 control pigs.

Studies on the efficacy of hyperbaric rendering procedures in inactivating bovine spongiform encephalopathy (BSE) and scrapie agents.

The efficacy of the procedures in use at the two rendering plants in the Netherlands was assessed on a laboratory-scale using procedures that simulated the pressure cooking part of the rendering process. A pool of bovine spongiform encephalopathy (BSE)-infected brainstem from the United Kingdom and a pool of scrapie-infected brainstem from Dutch sheep were used to spike the rendering materials. The mixtures were subjected to various time-temperature combinations of hyperbaric heat treatment related to the conditions used in Dutch rendering plants in the early 1990s, and to the combination of 20 minutes at 133 degrees C required by the EU Directive on rendering of 1996. The efficacy of the procedures in inactivating BSE or scrapie infectivity was measured by titrating the materials before and after heat treatment in inbred mice, by combined intracerebral and intraperitoneal inoculations at limiting dilutions. Two independent series of experiments were carried out. The design of the study allowed for minimum inactivations of up to 2.2 log (2.0 in the second series) to be measured in the diluted infective material and 3.1 log in the undiluted material. After 20 minutes at 133 degrees C there was a reduction of BSE infectivity of about 2.2 log in the first series (with some residual infectivity detected), and in the second series more than 2.0 log (with no residual infectivity detected). With undiluted brain material there was an inactivation of about 3.0 log (with some residual infectivity detected). With the same procedure, scrapie infectivity was reduced by more than 1.7 log in the first series and by more than 2.2 log in the second series. With undiluted brain material there was an inactivation of more than 3.1 log. In each case no residual scrapie infectivity was detected. The BSE agent consistently appeared to be more resistant to heat inactivation procedures than the scrapie agent, particularly at lower temperatures and shorter times.

Natural transmission of bovine leukemia virus in dairy and beef cattle.

Many potential routes of bovine leukemia virus (BLV) transmission are reviewed in this article. Vertical transmission, in utero, or through colostrum and milk, accounts for a relatively small proportion of infections. Iatrogenic horizontal transmission, through procedures permitting the transfer of blood between cattle, has been shown to be a major route of transmission in most settings. Contact transmission stems from a mixture of natural sources of blood, exudates, and tissues that enter the body through mucosal surfaces or broken skin. Careful analysis of management procedures and environmental conditions present in individual dairy and beef herds affords the greatest opportunity to develop effective BLV prevention programs.