Fecal Shedding of Salmonella in Horses Admitted to a Veterinary Teaching Hospital

Fecal samples were collected from 724 horses admitted to, and 232 horses hospitalized at, a veterinary teaching hospital between October 2000 and June 2001, and cultured for Salmonella. Salmonella was isolated on 24 occasions from 12 horses. S. Newport was the most commonly isolated serotype. The estimated prevalence (95% confidence interval [CI]) of Salmonella shedding on admission was 0.5% (0.1, 2.0). The estimated incidence rate of Salmonella shedding during hospitalization was 4.3% (95% CI, 2.2-8.1). The highest incidence of Salmonella shedding during hospitalization occurred during June 2001, but no significant (P > .5) temporal clusters of horses shedding Salmonella were detected.Horses shed Salmonella in their feces at a low rate. Horses shedding Salmonella occurred only sporadically and no obvious serotype pattern was observed. The occurrence of fecal shedding probably reflected the prevalence of inapparent Salmonella infection in the hospital source population, providing a baseline against which future potential outbreaks can be identified.

Introduction

Infection of horses by Salmonella organisms is a serious health issue. It is particularly troubling when outbreaks occur in hospitalized patients because these outbreaks can result in substantial economic losses and have a major impact on the welfare of patients.[1] Establishments with a high-density of horses, including veterinary teaching hospitals (VTHs) and private veterinary clinics, [1 and 2] are most vulnerable to outbreaks of disease attributable to Salmonella infection. Host susceptibility and environmental persistence of Salmonella are also factors contributing to outbreaks.Estimates of the prevalence of Salmonella-shedding horses admitted to veterinary hospitals have generally been made under outbreak conditions.[1] For example, between 1971 and 1982, 245 hospitalized horses (1.7%) at the University of California were found to shed Salmonella.[3 and 4] Three major outbreaks occurred during the study period, with no apparent periodicity. Between 1996 and 1999, 35 hospitalized horses (5.5%) at the Michigan State University were found to shed Salmonella.[5] One major outbreak occurred during the study period. Only one national survey of nonhospitalized horses in the United States for Salmonella infection has been undertaken: the prevalence of fecal shedding of Salmonella was estimated to be 0.8%, and the farm prevalence of shedding was 1.8%.[6]Many factors have been associated with the risk of Salmonella isolation from hospitalized horses, including diarrhea, fever, change in diet, large colon impaction, colic, withholding feed, feeding bran mash, antibiotic treatment, intubation with nasogastric tubes, and average daily ambient temperature.[7, 8, 9 and 10] Many of theses factors are thought to operate primarily through the effect of stress, increasing the susceptibility of horses to infection. Also, if a horse is infected by Salmonella but not shedding the organisms in its feces, the presence of stressors may reactivate fecal shedding. Most studies that have been conducted on risk factors for Salmonella shedding in horses have included horses with clinical salmonellosis, with or without inclusion of horses inapparently infected by Salmonella.[7, 8 and 10] Risk factors for Salmonella fecal shedding versus clinical salmonellosis have not been clearly delineated.An outbreak (epidemic) of disease can be defined as “an occurrence of disease in excess of its anticipated frequency.”[11] To more effectively identify future outbreaks of Salmonella infection in hospitalized horses, it is necessary to have accurate estimates of the prevalence of endemic fecal shedding of Salmonella in horses admitted to VTHs, and the incidence of fecal shedding during hospitalization. The aims of this study were to estimate the prevalence of fecal shedding in horses admitted to a VTH, to estimate the incidence of fecal shedding during hospitalization, and to describe the seasonal distribution of fecal Salmonella-shedding prevalence and incidence.

Materials and Methods

Study Design

Fecal samples were collected from horses admitted to the Purdue University VTH between October 12, 2000 and June 30, 2001. Horses admitted as inpatients were sampled at least on the day of admission, the day after admission, the day of discharge, and once or more in between. All horses admitted to the VTH during the study period were eligible to be sampled. In the case of mares accompanying sick foals, samples were also collected from the mare. Fecal samples were collected generally from freshly voided fecal material in stalls. Samples were stored at 4°C for up to 24 hours before processing.

Data Collection

For all horses included in the study, date of examination (outpatients) or date of hospitalization (inpatients) was recorded. For inpatients, date of discharge or date of death was also recorded. Horse characteristics were recorded as part of each horse's medical record, and included date of birth, sex (mare, stallion, gelding), and specific breed. The outcome of each admission (discharged alive, died, euthanized) and whether a necropsy was performed were also recorded. The number of samples collected per horse was recorded in a laboratory-reporting system, but specific date of collection of each sample (except for the first and last samples collected) was not routinely recorded.

Bacteriologic Cultures

All fecal samples were cultured for Salmonella species using standard techniques. Specimens were streaked onto brilliant green (BG) and xylose-lysine-tergitol (XLT-4) plates, and approximately 10 g of fecal material was put into 100 mL of tetrathionate Hajna broth. BG plates were incubated at 35° to 37°C for 18 to 24 hours and XLT-4 plates were incubated for 24 to 48 hours. Tetrathionate broth was incubated at 35° to 37°C for 24 to 48 hours, and then streaked to BG and XLT-4 plates. These plates were incubated as previously described. Suspect colonies on plates were subcultured and further identified by the Vitek GNI system. All Salmonella isolates were speciated and serotyped (National Veterinary Services Laboratory, Ames, Ia).

Data Analysis

The total number of horses examined (admissions), the total number of examinations (including admissions), the total number of horses hospitalized during the study period, and the number of samples collected per horse were calculated (Excel 2000, Microsoft Corp, Redmond, Wash) from recorded information. The frequency distributions of admissions (1-6) per horse, sex, breed, and patient outcome were calculated based on owner/horse identity and hospital record number, and the frequency distribution of number of samples collected per horse (nil to 8) was calculated from laboratory records and owner/horse identification and laboratory submission number. Length of hospitalization (days) was calculated from recorded date of hospitalization and date of discharge information, and was summarized by median and mean lengths of hospitalization and 95% confidence intervals (CIs), based on the Wilcoxon test (Minitab for Windows, Minitab Inc, State College, Penn) and the normal distribution (Statistix for Windows, Analytical Software, Tallahassee, Fla), respectively. Normality of the distributions of lengths of hospitalization and age were tested using the normal probability plot and Wilks-Shapiro statistic (Statistix).To estimate the incidence of Salmonella shedding, only hospitalized horses that were sampled on at least three occasions were included, because the sensitivity of culture is suboptimal and repeated attempts to culture Salmonella are necessary to increase the sensitivity of this technique.[12] The total number of days at-risk of shedding Salmonella was calculated as the sum of lengths of hospitalization. The incidence density rate (true incidence) of Salmonella shedding was calculated as

(No. horses detected shedding Salmonella)/(total No. horse-days at-risk)

and expressed as the number of horses shedding Salmonella per 1000 horse-days at-risk. For example, if 10, 10, and 30 horses were hospitalized for periods of 3, 6, and 9 days each, horse-days at-risk would be (10.3)+(10.6)+(30.9) = 360. If one case of Salmonella-shedding was detected in this group, the estimated incidence density rate would be one per (1000/360) 1000 horse-days AT-RISK = 2.8 per 1000 horse-days at-risk. Horses that were culture-positive on the first sampling were not considered incident cases of Salmonella-shedding, and therefore were not included in the numerator of the incidence density rate. Horses shedding Salmonella after hospitalization were assumed to have commenced shedding at the midpoint of their hospitalization, and therefore contributed half their length of hospitalization to the rate denominator. A 95% CI for the estimated incidence density rate was calculated assuming shedding Salmonella to be Poisson distributed.[13] Incidence-density rates were also calculated for each month of the study, the contribution of each horse to each month's horse-days at-risk being calculated on the basis of date of hospitalization and date of discharge information. Cumulative incidence (risk) rate (%) was calculated as described for the incidence density rate, except that the denominator used was the number of horses at-risk of Salmonella-shedding when hospitalized. For cumulative incidence rate, a 95% CI was calculated based on the binomial distribution.[14]The prevalence of Salmonella-shedding in horses admitted to the VTH was calculated as

(No. horses detected shedding Salmonella by culturewhen admitted)/(total No. horses admitted and sampled)

Ninety-five percent CIs for prevalence estimates were calculations based on the binomial distribution.[14]The temporal clustering of horses shedding Salmonella was investigated using the scan statistic.[15] For horses shedding Salmonella after hospitalization, the midpoint of their length of hospitalization was used as the date of first occurrence of Salmonella-shedding. The population at-risk used in these analyses was the monthly total number of horse-days at-risk. The occurrence of horses shedding Salmonella was assumed to be Poisson distributed, so the expected number of horses shedding Salmonella in any given time period was proportional to the incidence of Salmonella-shedding during the entire study period. The study period was scanned for clusters of horses shedding Salmonella using a scanning window of as much as 50% (130 days) of the time period (SatScan, Bethesda, Md).

Results

Between October 12, 2000 and June 30, 2001, 724 horses were admitted to the VTH. Six hundred and thirty-two horses (87.3%) were admitted only once during the study period; 69 (9.5%), 15 (2.1%), 2 (0.3%), 5 (0.7%), and 1 (0.1%) horses were admitted on 2, 3, 4, 5, and 6 separate occasions, respectively. Length of hospitalization was not recorded for 2 horses. Three-hundred and sixty (42.3%) of the 854 admissions performed did not result in hospitalization of the horse. The distribution of length of hospitalization of all horses hospitalized during the study is shown in Figure 1. The median and mean lengths of hospitalization (95% CI) were 3.0 (2.5, 3.5) and 4.3 (3.8, 4.7) days, respectively. The minimum and maximum lengths of hospitalization were 1 and 57 days. The distribution of lengths of stay was nonnormally distributed (Wilks-Shapiro statistic, 0.7317).     

LEPTOSPIRA INTERROGANS SEROTYPE HARDJO OUTBREAK IN A VICTORIAN DAIRY HERD AND ASSOCIATED INFECTION IN MAN

SUMMARY Leptospirosis associated with probable L. hardjo infection was investigated in a dairy herd in a coastal district of Western Victoria. Thirty-six of 110 cows suffered leptospiruria and mastitis characterised by flaccid udders and abnormal milk. One of two media used enabled the isolation of the organism from infected guinea pigs inoculated with fresh urine. Microscopic agglutination titres to L. hardjo were elevated during the outbreak. There was an associated human infection.     

Lessons learned from a strangles outbreak on a large Standardbred farm

Streptococcus equi subspecies (ssp.) equi infection (strangles) remains one of the most frequently diagnosed and costly infectious diseases of horses. Large breeding herds, where a disease outbreak competes for personnel and financial resources needed for foaling management, present a special challenge for equine practitioners. A 15‐month outbreak involving 62 clinical cases of strangles occurred on a large Standardbred breeding farm (average population of 1400 horses). Sixteen asymptomatic horses were found to be PCR (polymerase chain reaction)‐positive for S. equi ssp. equi. During the outbreak, serological samples from 48 clinically normal horses were found to be seropositive for S. equi ssp. equi, confirming herd‐wide exposure. After several clinical cases of strangles had been diagnosed, an intranasal S. equi ssp. equi vaccine was administered to clinically normal horses (n = 558) considered to be at risk of exposure. Strangles complications included 7 fatalities (none in vaccinated horses) and 6 cases of purpura haemorrhagica (4 in vaccinated horses). Midway through the outbreak, injectable, sustained release ceftiofur crystalline free acid (CCFA), given as an initial dose followed by a second dose 4 days later, was used exclusively for systemic antimicrobial treatment of clinically affected and PCR‐positive horses. This antimicrobial regimen coincided with a reduction in disease incidence and eventual resolution of the outbreak. Two horses with persistent guttural pouch infection were endoscopically confirmed as carrier horses. The herd history demonstrated that a strangles outbreak will often result in asymptomatic carrier horses and that identification and treatment of these horses are necessary to eliminate long‐term sources of infection. Ceftiofur crystalline free acid was found to be a suitable antimicrobial due to its activity against S. equi ssp. equi and the efficiencies associated with twice parenteral dosing during a 10‐day treatment period. Occurrence of purpura in 4 vaccinated horses suggests that vaccination should be reserved for healthy seronegative horses and avoided during an active outbreak.     

Efficacy of Tilmicosin Phosphate (Pulmotil® Premix) in Feed for the Treatment of a Clinical Outbreak of Actinobacilluspleuropneumoniae Infection in Growing–Finishing Pigs

A double‐blind randomized clinical trial was carried out to investigate the efficacy of tilmicosin (Pulmotil^® premix) for the treatment of a clinical outbreak of Actinobacillus pleuropneumoniae infection in growing–finishing pigs. The effects of tilmicosin administration in the feed at 400 mg/kg and an injection therapy of clinically diseased pigs with long‐acting oxytetracycline (Terramycine^® LA) at 20 mg/kg bodyweight were compared. Both groups, totalling 147 pigs, were compared during a medication period of 15 days and a post‐medication period of 11 days by means of different clinical and performance parameters. During the medication period, the tilmicosin group showed a significant advantage with respect to the number of new disease cases (P < 0.01), and a non‐significant advantage regarding the number of removed pigs (P=0.16), the number of sick pigs that recovered (P=0.27) and the time to recovery (P=0.42). During the post‐medication period, the pigs of the tilmicosin group showed numerical non‐significant benefits (P > 0.05) with respect to the clinical parameters. During the overall study period (26 days), the average daily gain and the feed conversion ratio were both significantly (P < 0.01) better in pigs from the tilmicosin group compared with pigs from the oxytetracycline group. This study demonstrated that in‐feed medication of tilmicosin at a dosage of 400 mg/kg is efficacious for the treatment of a clinical respiratory disease outbreak of A. pleuropneumoniae infection in growing–finishing pigs. Compared with oxytetracycline injection of clinically diseased pigs, the tilmicosin treatment is particularly beneficial in the prevention of new disease cases while increasing or maintaining the performance of the pigs.     

Use of a Dose–Response Model to Study Temporal Trends in Spatial Exposure to Coxiella burnetii: Analysis of a Multiyear Outbreak of Q Fever

The Netherlands underwent a large Q fever outbreak between 2007 and 2009. In this paper, we study spatial and temporal Coxiella burnetii exposure trends during this large outbreak as well as validate outcomes against other published studies and provide evidence to support hypotheses on the causes of the outbreak. To achieve this, we develop a framework using a dose–response model to translate acute Q fever case incidence into exposure estimates. More specifically, we incorporate a geostatistical model that accounts for spatial and temporal correlation of exposure estimates from a human Q fever dose–response model to quantify exposure trends during the outbreak. The 2051 cases, with the corresponding age, gender and residential addresses, reside in the region with the highest attack rates during the outbreak in the Netherlands between 2006 and 2009. We conclude that the multiyear outbreak in the Netherlands is caused by sustained release of infectious bacteria from the same sources, which suggests that earlier implementation of interventions may have prevented many of the cases. The model predicts the risk of infection and acute symptomatic Q fever from multiple exposure sources during a multiple‐year outbreak providing a robust, evidence‐based methodology to support decision‐making and intervention design.     

Review of the epidemiology and infection control aspects of nosocomial Salmonella infections in hospitalised horses

Outbreaks of nosocomial Salmonella infections in hospitalised horses can occur when surveillance and infection control protocols are not in place, or not well structured and enforced. The aim of this article is to present a review of published studies that have contributed to the literature of the epidemiology and infection control aspects of nosocomial Salmonella infections in hospitalised horses. The review highlights important elements that must be taken into consideration during the formulation, implementation and evaluation of a hospital surveillance and infection control programme designed to reduce the risk of an outbreak of nosocomial Salmonella infection in hospitalised horses.     

Clinical signs of West Nile virus encephalomyelitis in horses during the outbreak in Israel in 2000

Between August and October 2000, 76 horses were reported by veterinary practitioners as having signs of a neurological disorder, varying from an involvement of the spinal cord alone to the entire central nervous system; 15 of the horses died or were euthanased as a result of their grave prognosis or secondary complications. At the same time, an outbreak of West Nile virus infection affected people and birds, principally domestic geese. West Nile virus was isolated from four of the horses with encephalomyelitis and five other horses seroconverted, indicating that the virus was the probable cause of the outbreak in horses. Three of the cases from which the virus was isolated are described briefly and one case is described in detail. This horse behaved abnormally and had general proprioceptive deficits in all four limbs. Its neurological condition deteriorated after two days and severe inspiratory dyspnoea due to a failure to abduct the arytenoids necessitated a tracheostomy. It died on the fourth day and histological lesions were observed in the brain stem and grey matter of the spinal cord.     

The population of a high-virulence strain of <Emphasis Type="Italic">Salmonella enterica</Emphasis> serovar Enteritidis in subcutaneously infected partridge: a quantitative time-course study using real-time PCR

This research was undertaken to determine the population of a high-virulence strain of Salmonella enterica serovar Enteritidis in partridge by a fluorescent quencher PCR assay and to correlate these findings with the results obtained from the immunohistochemical localization and histopathological examinations of selected Salmonella enterica serovar Enteritidis-infected tissues. To make the results meaningful, a side-by-side bacteriology method (indirect immuno-fluorescent antibody staining) was performed too. The results of indirect immuno-fluorescent antibody staining and immunohistochemical localization were similar to the fluorescent quencher PCR assay. The time course of the appearance of bacterial antigens and tissue lesions in various tissues was coincident with the levels of the bacterial DNA loads at the infection sites. This suggests that Salmonella enterica serovar Enteritidis loads in internal organs are closely correlated with the progression of the infection.     

An unprecedented cluster of Australian bat lyssavirus in Pteropus conspicillatus indicates pre‐flight flying fox pups are at risk of mass infection

In November 2017, two groups of P. conspicillatus pups from separate locations in Far North Queensland presented with neurological signs consistent with Australian bat lyssavirus (ABLV) infection. These pups (n = 11) died over an 11‐day period and were submitted to a government laboratory for testing where ABLV infection was confirmed. Over the next several weeks, additional ABLV cases in flying foxes in Queensland were also detected. Brain tissue from ABLV‐infected flying foxes during this period, as well as archived brain tissue, was selected for next‐generation sequencing. Phylogenetic analysis suggests that the two groups of pups were each infected from single sources. They were likely exposed while in crèche at night as their dams foraged. This study identifies crèche‐age pups at a potentially heightened risk for mass ABLV infection.     

Estimates of within-herd incidence rates of Mycobacterium bovis in Canadian cattle and cervids between 1985 and 1994

We analysed the individual-animal data from six of the nine outbreaks of tuberculosis in Canadian cattle and cervids from 1985 to 1994. A “positive/reactor” animal was one which had either a positive culture or a positive or suspicious reaction on a mid-cervical, comparative cervical, or gross or histopathological test for tuberculosis. Individual-animal data were collected only for herds which had one or more positive/reactor animals. Data were collected from the outbreak records in the Regional or District offices of Agriculture and Agri-food Canada’s Animal and Plant Health Directorate. The within-herd spread of Mycobacterium bovis was studied by determining the most-likely date at which the herd was first exposed to M. bovis and the number of reactions which had developed by the time the herd was investigated. The animal-time units at risk in the herd were probably overestimated, resulting in conservative estimates of the within-herd incidence rates. Negative-binomial regression was used to investigate factors which might have influenced the within-herd spread of tuberculosis. Increasing age appeared to be a risk factor for being a positive/reactor animal. When compared to animals 0–12 months old, animals 13–24 months old had an incidence rate ratio (IRR) of 7.6, while animals >24 months old had an IRR of 10.4 (p=0.009). Actual and predicted incidence rates for tuberculosis in mature (>24 months old) animals were calculated. Actual and predicted incidence rates were similar for cervids, within an outbreak. There was more variability between actual and predicted rates in the dairy and beef animals. In the one outbreak (Ontario) where there were positive/reactor cervid, dairy and beef herds, the actual incidence rate for cervids (IR=9.3 cases per 100 animal-years) was almost twice that of dairy cattle (IR=5.0) and three times that of beef cattle (IR=3.1).     

Climatic factors associated with the infection of herds of cattle with bluetongue viruses

The incidence of bluetongue virus infection of 15 cattle herds in Queensland, Australia, was determined by a serum neutralization test. The maximum temperature (°C), minimum temperature (°C) and rainfall (mm) data were obtained from the meteorological recording stations closest to each herd. Using unweighted least-squares regression analysis, the best statistical model explaining the most variability in the herd incidence rate included the ratio between the maximum and minimum temperature recorded at both 1 month and 6 months preceding seroconversion, and rainfall recorded at both 2 months and 6 months preceding seroconversion. More than 90% of the variability in the incidence of bluetongue virus infection in the herds was explained by the model, a considerable improvement on previous models that used prevalence data. The prospective nature of the study also supports a strong causal relationship between climatic factors and the occurrence of infection in cattle herds.Abbreviations SN serum neutralization - R _infa ^sup2 adjusted coefficient of multiple determination - AIC Akaike's information criterion - FPE Akaike's final prediction error - PRESS predicted sum of squares     

Idiopathic Canine Laryngeal Paralysis as One Sign of a Diffuse Polyneuropathy: An Observational Study of 90 Cases (2007–2013)

Objective

To determine survival and incidence of complications in dogs with idiopathic laryngeal paralysis (ILP) and concurrent neurologic signs.

Study Design

Observational study.

Animals

Dogs (n = 90) with ILP.

Methods

Medical records (January 2007–June 2013) of dogs with ILP were reviewed. Neurologic comorbidities, including pelvic limb neurologic abnormalities and esophageal abnormalities were identified. Using medical record information and client interviews, the relationship between these comorbidities and postoperative survival (primary outcome measure) and postoperative complications (secondary outcome measure) was identified.

Results

Dogs that had surgical correction of ILP had a 2.6‐fold reduction in the hazard of death throughout the study period (HR = 2.6; 95% CI: 1.34–4.84, P = .006). Owner assessed patient quality of life (10‐point scale) increased by an average of 4.1 ± 1.4 units immediately postoperatively, and 4.9 ± 0.9 units until death or followup compared with preoperative values. Thirty‐five of 72 dogs available for followup had evidence of diffuse neurologic comorbidities. Overall complication rate for dogs with neurologic comorbidities was 74%, compared with 32% for dogs without neurologic comorbidities. Presence of any neurologic comorbidity was associated with a significantly greater odds of any complication (OR = 4.04; 95% CI: 1.25–13.90, P = .019) as well as recurring complications (OR = 8.00; 95% CI: 1.49–54.38; P = .015).

Conclusion

Surgical correction of ILP was positively associated with survival, and dogs with neurologic comorbidities were at greater risk for developing postoperative complications.

     

The prophylactic effect of a dry-cow antibiotic against Streptococcus uberis

The prophylactic use of a dry-cow antibiotic for reducing the incidence of mastitis due to Streptococcus uberis was studied in four seasonally calving dairy herds involving 378 cows. The treatment was a long-acting dry-cow antibiotic preparation administered immediately after the last milking of lactation. New intramammary infections were identified by comparing the bacteriological status of quarters at drying off with that after calving, or through manual udder palpation during the dry period. The administration of dry-cow antibiotic to uninfected quarters at drying off reduced the overall incidence of new infections with Streptococcus uberis from 12.3% for untreated quarters to 1.2% of quarters (p<0.01). The reduction was significant (p<0.01) for both dry-period and post-calving infections. The susceptibility of uninfected quarters to new infection by Streptococcus uberis appeared to be unrelated to the infection status of a cow at drying off. Clinical infections during the dry period were most prevalent (97%) in quarters identified as having open teat canals. Fewer open teat canals (p<0.05) were observed among antibiotic treated quarters over the first 4 weeks of the dry period. Treated quarters had a lower (p<0.05) incidence of new clinical infection during the ensuing lactation and lower somatic cell counts. This did not affect production levels of milk, milk fat or protein. The results clearly indicated a prophylactic benefit for the dry cow antibiotic treatment against new Streptococcus uberis infections during the dry period.     

Novel findings from a beta coronavirus outbreak on an American Miniature Horse breeding farm in upstate New York

This case report describes an outbreak and novel findings associated with a beta coronavirus (BCoV) infection that occurred on an American Miniature Horse (AMH) breeding farm in upstate New York, in January and February of 2013. Twenty-nine AMH and one donkey were present on the farm when the outbreak occurred. One 10-year-old Quarter Horse mare, stabled at a separate location and owned by an employee of the farm, also tested positive. A polymerase chain reaction (PCR) assay for the detection of BCoV was performed at the Animal Health Diagnostic Center (AHDC) at Cornell on all faecal samples. The PCR assay used detects multiple beta coronaviruses, including, but not limited to, equine enteric coronavirus (ECoV). Novel findings regarding this BCoV infection in horses were recognised in this outbreak study. To the authors’ knowledge, this is the largest outbreak of BCoV described thus far in a closed herd on a single premise. The case fatality rate was 0% unlike that described in a previous outbreak of ECoV involving miniature horses and a miniature donkey (Fielding et al. 2015). The morbidity rate was lower in this outbreak than in previously described studies (Oue et al. 2013; Pusterla et al. 2013). This outbreak also demonstrated the potential for BCoV transmission via farm personnel. The duration of shedding of virus in the faeces among some asymptomatic horses in this outbreak was longer than previously described clinical cases of ECoV (Pusterla et al. 2013; Nemoto et al. 2014). This study suggests that asymptomatic animals may play a role in the maintenance of BCoV during an outbreak; therefore, the need for diagnostic testing of both clinically affected and apparently clinically normal horses on a premises followed by appropriate biosecurity and control measures.     

A syndrome of facial paralysis of dairy calves in the Franklin district of New Zealand

AIM: To determine the aetiology of a syndrome characterised by facial paralysis in calves (facial paralysis syndrome; FPS); describe the epidemiology of the syndrome on an affected case farm; and define the intra-farm prevalence of affected calves, and inter-farm prevalence of affected dairy farms, in the Franklin district of New Zealand.

CASE HISTORY AND CLINICAL FINDINGS: An investigation was carried out on a town-supply dairy farm experiencing an outbreak of FPS in calves during the autumn of 2007, following a previous outbreak during the spring of 2006; 21 calves were affected in both outbreaks. Post-mortem examinations of three affected calves revealed no infectious aetiological agent in neurological tissues despite tests for viruses, bacteria and Mycoplasma species. Tests on hepatic tissues for vanadium toxicity were inconclusive.

SURVEY OF DAIRY FARMS: Results from a postal survey of 177/325 (54%) farms established the yearly prevalence of affected farms, based on farmer diagnosis, was 11%, and there was a median two (range 1–25) affected calves on those farms. There was no evidence of spatial clustering of affected farms after accounting for the underlying farm density, or of an increase in the number of affected farms between 2003 and 2007.

CLINICAL RELEVANCE: Facial paralysis syndrome is an unusual condition that has not been reported in other districts of New Zealand or in other countries. It is probable that this syndrome will continue to occur at a low to moderate prevalence, and have a significant impact on a small number of farms.     

Habitat evaluation for outbreak of Yangtze voles (Microtus fortis) and management implications

Rodent pests severely damage agricultural crops. Outbreak risk models of rodent pests often do not include sufficient information regarding geographic variation. Habitat plays an important role in rodent–pest outbreak risk, and more information about the relationship between habitat and crop protection is urgently needed. The goal of the present study was to provide an outbreak risk map for the Dongting Lake region and to understand the relationship between rodent–pest outbreak variation and habitat distribution. The main rodent pests in the Dongting Lake region are Yangtze voles (Microtus fortis). These pests cause massive damage in outbreak years, most notably in 2007. Habitat evaluation and ecological details were obtained by analyzing the correlation between habitat suitability and outbreak risk, as indicated by population density and historical events. For the source‐sink population, 96.18% of Yangtze vole disaster regions were covered by a 10‐km buffer zone of suitable habitat in 2007. Historical outbreak frequency and peak population density were significantly correlated with the proportion of land covered by suitable habitat (r = 0.68, P = 0.04 and r = 0.76, P = 0.03, respectively). The Yangtze vole population tends to migrate approximately 10 km in outbreak years. Here, we propose a practical method for habitat evaluation that can be used to create integrated pest management plans for rodent pests when combined with basic information on the biology, ecology and behavior of the target species.     

Review of African swine fever outbreaks history in South Africa: From 1926 to 2018

The article reviews the outbreaks and distribution of African swine fever (ASF) in South Africa since the first probable outbreak that occurred in the Koedoesrand Ward in 1926. Retrospective data on the ASF outbreaks in South Africa were obtained from the World Organisation for Animal Health (OIE) disease database and the South African veterinary services annual reports in addition to published articles and online sources. South Africa has experienced many outbreaks that can be divided into 2 time periods: the period before the development of the OIE diseases database (1993) and the period after. More than 141 outbreaks of ASF were reported during the first period. Since the development of OIE disease database, 72 outbreaks directly involving 2968 cases, 2187 dead and 2358 killed pigs mainly in smallholder pig farms were reported. The median number of cases for a given ASF outbreak is 17, but in 50% of outbreaks no pigs were killed for prevention. The most important ASF outbreak was reported in April 2014 in the Greater Zeerust district (North West province) involving 326 cases and 1462 killed pigs. However, the outbreak with highest mortality involving 250 pigs was reported in 2016 (Free State province). According to phylogenetic analysis, nine p72 genotypes (I, III, IV, VII, VIII, XIX, XX, XXI and XXII) have been identified in South Africa. Season-wise, more outbreaks were recorded during summer. It was also observed that the OIE disease database could contain errors that would have been introduced through compiled forms at country level. Spatiotemporal studies on ASF outbreaks in South Africa are therefore required in order to assess statistically and quantitatively the clustering of outbreaks over space and time.     

Perception of Equine Practitioners Regarding the Occurrence of Selected Equine Neurologic Diseases in the Northeast Over a 10-Year Period

A survey was developed to examine the perception of equine practitioners regarding the occurrence of five equine neurologic diseases in the northeastern United States over the 10-year period between June 1, 1997 and June 1, 2007. This information was then compared with trends at Cornell University's Equine Hospital during the same time span, which in general agreed with practitioners' opinions. Equine herpes virus-1 (EHV-1) neurologic disease, equine motor neuron disease (EMND), and equine protozoal myelitis (EPM) have historic and current relevance. Results showed that the frequency of EMND and EPM has remained relatively stationary or decreased somewhat, whereas the frequency of the neurologic strain of EHV-1 may have increased slightly over the last decade. Less historical information on clinical disease associated with Borrelia burgdorferi infection (Lyme disease) and Parelaphostrongylus tenuis exists; however, results suggest that P. tenuis in the equine is presently emergent. Opinions regarding the existence and rate of occurrence of clinical borreliosis in horses appear divided. A better understanding of the frequency with which these diseases occur, as well as possible associated positive risk factors, will aid the equine practitioner in making an appropriate diagnosis in cases of neurologic disease in their equine patients.