An epidemiological study of winter dysentery in fifteen herds in France

Winter dysentery is a highly contagious disease of cattle seen most often during the winter months. In the course of an epidemiological study, the management, production, hygiene and previous diseases in 15 herds were characterized by 32 variables. Each herd was then visited twice a week for 8 weeks and 8 to 10 cows were clinically examined during each visit. Winter dysentery occurred in half of the herds during the survey.All data were analysed by classical statistical methods and by multivariate analysis.Mild or severe disease provoked nasal discharge and was associated with significant economic loss. Winter dysentery outbreaks appeared to be associated with small farms in which the area available per cow is either too small or too large, the presence of coronavirus in the faeces and variations in the temperature of the stable and of the drinking water.     

Sheep scab outbreaks in Great Britain between 1973 and 1992: spatial and temporal patterns.

In January 1973, the mange mite Psoroptes ovis was found in a sheep flock in Lancashire, UK after a 20 year period of eradication. Over the next 20 years, a total of 1480 flock outbreaks were reported, until June 1992 when the control of sheep scab was deregulated. The spatial and temporal patterns of the number of outbreaks in each month over this period were analysed using time series methods, a geographical information system (GIS) and second order approaches to the exploration of space-time interaction (K-function analysis). The monthly time series displays clear evidence of seasonal cyclicity, with most outbreaks being reported in the winter months. After removal of the summer compulsory dip in 1988 however, there is evidence of a change in the seasonal pattern, with more cases being reported in the autumn months. There is also evidence of a contribution from a sinusoidal wave with a period of 8 years, which roughly corresponds to the major changes in the national control policy. The spatial pattern also appears to expand and contract on a roughly 4 year cycle, again reflecting the oscillating periods of success and failure. Examination of the spatial and temporal pattern revealed strong evidence of space-time clustering (p < 0.001) and a major contribution to the pattern from very local (< 12 km) spread within 5 months of an arbitrary outbreak.     

Detection of space-time clusters and epidemiological examinations of scabies in chamois

In this paper some methodological approaches towards the detection of temporal, spatial and space-time clusters are presented and discussed in context with epidemiological factors of scabies in chamois. This presentation comprises in particular the use of the Scan Test (Wallenstein, 1980) for the detection of temporal clusters and the tests developed by Knox (1964) and Mantel (1967) for the testing of spatiotemporal interactions. Between 1952 and 1998 a total of 1689 cases of scabies in chamois and six cases in ibex were documented in 137 game preserves of the Austrian province of Styria. The evaluations indicate the presence of spatial and temporal clusters. Some possibilities for the spread of scabies in chamois are presented and reveal ibex as a probable vector for scabies transmission between chamois populations. The information may lead to strategies for controlling the spread of the disease.     

Spatial and spatial-temporal clustering analysis of hemorrhagic disease in white-tailed deer in the southeastern USA: 1980-2003

We used the space-time K function and Kulldorff's scan statistic to analyze the spatial and spatial-temporal clustering of hemorrhagic disease (HD) in white-tailed deer in Alabama, Georgia, South Carolina, North Carolina, and Tennessee. The HD occurrence data were binary presence/absence data acquired annually on a county basis from 1980 to 2003. Space-time K function was employed to globally examine the existence of spatial-temporal clustering in the HD data. Three approaches of Kulldorff's scan statistic, i.e., spatial clustering analysis for the entire period, spatial-temporal clustering analysis, and spatial clustering analysis by individual years, were applied to detect potential HD clusters. Statistically significant spatial clusters and spatial-temporal clusters were detected in the five southeastern states during the 24-year study period. Some clusters were observed in multiple years. Clusters were most evident in west Alabama, south Alabama, central South Carolina, and along the border between South Carolina and North Carolina. The identification of HD clusters may provide a means to better understand the causal factors related to the HD outbreaks. Results also have potential application in improving or designing effective surveillance programs for this disease.     

Evaluation of temporal and spatial clustering of horses with Corynebacterium pseudotuberculosis infection

OBJECTIVE: To determine whether horses with Corynebacterium pseudotuberculosis infections that were examined at a veterinary medical teaching hospital between July 1, 1992, and June 30, 1994 had patterns of temporal or spatial clustering. ANIMALS: 134 case and 800 control horses randomly selected from all non-case horses admitted during the study period. PROCEDURES: Admission date and geographic location were determined. Scan, Cuzick & Edwards', and Knox tests were applied to determine whether case horses had patterns of temporal or spatial clustering. RESULTS: For all windows > or = 3 days (134 case horses) and > or = 7 days (subset of 69 case horses), results of the Scan test were significant. Results of Cuzick & Edwards' test were significant for all data sets. A significant spatial cluster of case horses was observed for October, November, and December 1992. Results of the Knox test were significant for temporal intervals between 7 and 56 days and spatial intervals between 4.3 and 6.5 km. Higher Knox(x) proportions were observed for temporal intervals of 0 to 7, 8 to 14, 22 to 28, and 29 to 35 days. CONCLUSIONS: Significant spatial and temporal clustering of horses with C pseudotuberculosis infection was detected. CLINICAL RELEVANCE: Analysis of the results strongly indicates that this disease is directly or indirectly (ie, short distance and time) transmitted. In addition, data analyses indicated an incubation period of 3 to 4 weeks. The disease could be transmitted through horse-to-horse contact or from infected to susceptible horses via insects, other vectors, or contaminated soil.     

Winter dysentery in dairy herds: electron microscopic and serological evidence for an association with coronavirus infection.

Faeces and, or, paired sera were collected from cows in six dairy herds with classical winter dysentery. Similar samples were collected from cows in three other dairy herds experiencing non-haemorrhagic diarrhoea during the survey period. Coronavirus was the only enteric pathogen identified by immune electron microscopy (IEM) in all six outbreaks, occurring in 26 of 29 (90 per cent) of the affected cows and in one of 11 normal cows from the same herds. Nineteen of 26 affected cows (73 per cent) developed greater than four-fold increases in neutralising antibody titres to the Mebus strain of bovine coronavirus, compared with two of eight normal cows in the same herds. No cows showed greater than four-fold increases in antibody titres to bovine virus diarrhoea virus. None of the cows from the three herds with non-haemorrhagic diarrhoea shed coronavirus in faeces detectable by IEM or developed greater than two-fold rises in coronavirus antibody titres in paired sera. No enteric pathogens were identified in two of the herds. However, two cows in the third herd shed a group B rotavirus detected by IEM. These findings provide additional evidence for a possible role for bovine coronavirus in the aetiology of winter dysentery. Furthermore, this is the first report of a group B rotavirus associated with diarrhoea in adult cattle.     

Analysis of time-space clustering in veterinary epidemiology

Techniques useful for investigating time–space interaction in the clustering of events in veterinary epidemiology — the Mantel test, Barton’s method, nearest-neighbour test and Knox’s test — are described. The use of these techniques is demonstrated by the analysis of a data set (containing blowfly catches on a commercial sheep property located in Tasmania, Australia, during the period December 1997–May 1998) in which clustering was apparent. Significant (P<0.05) clustering of blowfly catches in the data set was only detected by Knox’s test. The use of Knox’s test provided an insight into the possible clustering of blowfly catches over short (≤3 km) spatial and temporal (≤1 month) distances. Results demonstrate that several techniques should be used when attempting to identify and describe whether events are clustered in time and space (to maximise the power of the analysis). Also, it is important to consider the spatial and temporal models implicit in techniques chosen when interpreting results of analysis.     

Hydrographics and the timing of infectious salmon anemia outbreaks among Atlantic salmon (Salmo salar L.) farms in the Quoddy region of Maine, USA and New Brunswick, Canada

Infectious salmon anemia (ISA) has caused severe morbidity and mortality in farmed Atlantic salmon in North America, Norway, Scotland and the Faroe Islands. The Quoddy region of Maine, United States of America (USA), and New Brunswick (NB), Canada is characterized by extensive tidal mixing and close proximity between farms. This region is also prone to recurrent appearances of ISA, though control measures limit disease spread and severity on infected farms. We conducted a retrospective longitudinal analysis of the apparent impact of hydrographics on the incidence and timing of ISA outbreaks on Atlantic salmon (Salmo salar L.) farms in the Quoddy region from May 2002 to August 2004. A time-series cross-sectional regression of 32 farms over 28 months demonstrated a limited, but statistically significant, spatio-temporal clustering of ISA outbreaks linked hydrographically. New outbreaks correlated temporally with those occurring on-site 1 and 3 months prior, and those occurring within one tidal-excursion upstream the same month. Other risk factors included holdover of previous year-class fish, wharf sharing, and possibly harvests of cages infected in previous months. Conclusions suggest that tidal dispersion does play a role in ISAV transmission in the Quoddy region. Dispersal of free virus and/or tidal distribution of lice or other hydrographically influenced vectors or fomites could all contribute to the spatio-temporal patterns described.     

Association of diarrhea in cattle with torovirus infections on farms.

An epidemiologic survey was performed to determine the incidence of torovirus infections in 2 disease entities of cattle: diarrhea of replacement calves up to 2 months old, and winter dysentery of adult cattle. Samples were obtained from 187 diarrheal and 115 healthy calves from 15 farms, as well as 149 diarrheal and 67 healthy cows from 27 farms with or without winter dysentery. Enzyme-linked immunosorbent assays for detection of torovirus, rotavirus, and coronavirus antigen in feces, and of torovirus and coronavirus antibodies in serum were used to monitor infections in these groups. Torovirus was detected in 9 of the 15 farms in the study, and in 6% of calves with diarrhea, which was significantly higher than in healthy calves (2%). Seroconversion to torovirus was found significantly more often after winter dysentery episodes than on farms without a disease history; coronavirus seroconversion was less common.     

Observations on acute salmonellosis in four Waikato dairy herds

Acute epidemic salmonellosis was investigated in the winter of 1978 in 4 dairy herds in the Waikato district. The outbreaks involved pregnant or recently calved cows. Calves were affected on only one farm. Salmonella bovismorbificans was isolated from the faecal, uterine and environmental samples from the herd most severely affected. In this herd 20, (20%) of the cows died; 10 calves were either born dead or died soon after birth; and 10 cows were culled as unlikely to return to production. S. typhimurium was involved in the outbreaks in the other 3 herds and from one of these farms salmonellae were isolated from the faeces of the 2 farm dogs and from a 12-month-old infant with dysentery. Salmonellae were recovered from all of the clinically ill cows and from 36% of the asymptomatic animals. Salmonellae were widespread on the properties and were isolated from 81% of soil samples; 36% of drain swabs; and from all the pairs of rubber boots worn while collecting samples.     

Serological comparison of French WD-42 enterovirus isolate with bovine winter dysentery in New York State.

Forty-eight acute and convalescent paired serums from 10 dairy cattle herds naturally infected with winter dysentery and 10 paired serums from laboratory infected heifers were tested for antibody to bovine enterovirus WD-42 which reportedly reproduced the disease syndrome in France. Only 3 naturally infected and 1 experimentally infected animals had 2-fold antibody responses. No clinical symptoms were observed in 2 steers inoculated with WD-42. Each had a 4-fold or greater antibody response to the virus. Results indicate that the winter dysentery syndrome observed in New York is produced by an agent other than WD-42 virus and that it is produced by an agent other than an enterovirus.     

Space-time interaction as an indicator of local spread during the 2001 FMD outbreak in the UK

During the 2001 FMD outbreak in the UK, decisions on the level of implementation of control measures were supported by predictive models. Models were mainly used as macro-level tools to predict the behaviour of the disease in the whole country rather than at the local level. Here we explore the use of the magnitude and characteristics of the space-time interaction as an indicator of local spread and, indirectly, of the effectiveness of control measures aimed at reducing short-range transmission during the course of a major livestock disease epidemic. The spatiotemporal evolution patterns are described in the four main clusters that were observed during the outbreak by means of the hazard rate and space-time K-function (K(s,t)). For each local outbreak, the relative measure D(0)(s,t), derived from K(s,t), which represents the excess risk attributable to the space-time interaction was calculated for consecutive 20-day temporal windows to represent the dynamics of the space-time interaction. The dynamics of the spatiotemporal interaction were very different among the four local clusters, suggesting that the intensity of local spread, and therefore the effectiveness of control measures, markedly differed between local outbreaks. The large heterogeneity observed in the relative impact of being close in time and space to an infected premises suggests that the decision making in relation to control of the outbreak would have benefited from indicators of local spread which could be used to complement global predictive modelling results. Despite its limitations, our results suggest that the real-time analysis of the space-time interaction can be a valuable decision support tool during the course of a livestock disease epidemic.     

Summary of foot-and-mouth disease outbreaks reported in and around the Kruger National Park, South Africa, between 1970 and 2009

Information with regard to foot-and-mouth disease (FMD) outbreaks that occurred in the Kruger National Park (KNP) and adjacent areas of South Africa between 1970 and 2009 was collected from reports and files of various government departments and collated into one report. The collected data were summarised in a table and assessed for patterns. Fifty-one FMD outbreaks occurred during this period in the target area, of which 16 were SAT 1, 31 were SAT 2,4 were SAT 3 and 3 were not serotyped. No pattern could be discerned although SAT 1 outbreaks occurred more frequently in the summer months while more SAT 2 outbreaks occurred in winter.     

Techniques for analysis of disease clustering in space and in time in veterinary epidemiology

Techniques to describe and investigate clustering of disease in space — the nearest-neighbour test, autocorrelation, Cuzick-and-Edwards’ test and the spatial scan statistic — and in time — the Ederer–Myers–Mantel test and the temporal scan statistic — are reviewed. The application of these techniques in veterinary epidemiology is demonstrated by the analysis of a data set describing the occurrence of blowfly strike — both body strike and breech strike — between August 1998 and May 1999 in 33 commercial sheep flocks located within two local government areas of southeastern Queensland, Australia. By applying a combination of these methods, the occurrence of blowfly strike in the study area is well-characterised in both space and time. Guidelines for investigating disease clusters in veterinary epidemiology are discussed.     

奶牛冬痢病的诊断与防治

奶牛冬痢病是一种世界范围内常见的急性肠道传染病,以患病个体排棕色稀便和下痢便血为主要特征,发病突然,传播速度快,可显著降低奶牛产量,给养殖户造成严重的经济损失。对该病要严格预防,一旦发病要早发现,早治疗,切断病原传播途径,防止传染。同时,要加强奶牛场的综合管理。     

Dysentery in calves caused by an atypical strain of Escherichia coli (S102-9)

Dysentery lasting 4-8 days was produced in five 4-day-old colostrum-fed calves, after inoculation with an atypical strain of Escherichia coli S102-9; peak excretion of S102-9 occurred during the period of dysentery. Two calves were killed when clinical signs were most severe and bacteria were seen attached to the surfaces of enterocytes in the large intestine; microscopic lesions were seen in these areas. The lesions were identical to those previously reported in a natural outbreak of dysentery in calves, from which E. coli S102-9 was isolated, and to those seen in gnotobiotic calves experimentally infected with S102-9. Reinfection of the three surviving calves 16-20 days later with S102-9 and primary infection of two calves aged 24 and 51 days did not cause dysentery. Four of 659 coliforms isolated from field outbreaks of calf diarrhoea resembled the atypical strain S102-9. These four isolates and S102-9 did not produce heat-stable enterotoxin, but all produced a toxin cytopathic for Vero and HeLa cells. Two of the four isolates were inoculated alone into 4-day-old gnotobiotic calves deprived of colostrum; neither calf developed dysentery but microscopic lesions identical to those produced by S102-9 were detected in the large intestines of both animals.     

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.