An ovine hepatotoxicosis caused by the plant Hertia pallens (DC.) Kuntze (Asteraceae)

A field outbreak of Hertia pallens poisoning in sheep is described. The hepatotoxicity of the plant was experimentally demonstrated in 7 sheep which developed lesions that ranged from a diffuse degeneration to centrilobular necrosis. These lesions occasionally extended to the midzonal area of the lobules. In addition to a lung oedema, a diffuse mononuclear interstitial pneumonia was present in 3 of the sheep. Botanical, clinical and pathological data are given.     

Foot-and-mouth disease virus (O/UKG/2001) is poorly transmitted between sheep by the airborne route

Foot-and-mouth disease virus (FMDV) can be spread by the airborne route and therefore atmospheric dispersion models have been developed to predict where the virus might spread during a disease outbreak. Airborne transmission between sheep of the FMDV strain involved in the outbreak in Europe in 2001 (O/UKG/2001) was studied experimentally. Recipient animals were exposed to two donor sheep excreting virus for 2, 4, 6, 8 or 24 h. Although FMDV was detected in air samples collected during challenge, none of the recipient sheep became infected. These data suggest that O/UKG/2001 is not efficiently transmitted by the airborne route between sheep.     

A field outbreak in Ile-de-France sheep of a cardiotoxicosis caused by the plant Pachystigma pygmaeum (Schltr) Robyns (Rubiaceae)

A field outbreak of Pachystigma pygmaeum intoxication in sheep is described. Noteworthy clinical signs were: respiratory distress, apathy and subcutaneous oedema of mainly the head. Gross changes included cardiomegaly, centrilobular hepatic necrosis and effusion of body cavities. Microscopically myocardial fibrosis, affecting predominantly the endocardium of the apex, left free ventricular wall and interventricular septum, was most striking in the majority of animals, whilst myofibre atrophy was present in 1 sheep.     

Salmonella gona infection in sheep

A field outbreak of salmonellosis due to Salmonella agona in sheep and some subsequent experimental work is described. While the field outbreak in pregnant ewes and neonatal lambs caused severe losses the experimental disease in non-pregnant sheep was mild and transient. S agona was not isolated from the carcases of the experimental sheep killed after 28 days post infection but it persisted for 69 days in the faeces of one ewe which was kept alive for three months. Media comparisons indicated that selenite enrichment broths incubated at 43 degrees C and plated on to brilliant green agar gave the most satisfactory cultural results.     

Field observations during the Bluetongue serotype 8 epidemic in 2006. II. Morbidity and mortality rate, case fatality and clinical recovery in sheep and cattle in the Netherlands

Data collected in the Netherlands during the Bluetongue serotype 8 (BTV-8) epidemic indicated that in outbreak cattle herds, predominantly dairy and nursing cows were clinically affected and not young stock, beef cattle, beef calves, or breeding animals. In outbreak sheep flocks, mainly ewes and - if present - rams, were clinically affected and not the lambs. Median morbidity rate in outbreak herds was 1.85 per 100 sheep-month at risk and 0.32 per 100 cattle-month at risk for sheep and cattle, respectively. The mean proportion of BT-affected animals in outbreak herds that recovered from clinical disease was approximately eight times higher for cattle compared to sheep in the Netherlands. Median mortality rate in outbreak herds was 0.5 per 100 sheep-month at risk of dying and 0 per 100 cattle-month at risk of dying for sheep and cattle, respectively. Median recovery time of both sheep and cattle that recovered from clinical disease in outbreak herds was 14 days. Median case fatality was 50% in sheep outbreak flocks and 0% in outbreak cattle herds. It is concluded that morbidity and mortality in outbreak cattle herds was very limited during the BTV-8 epidemic in the Netherlands in 2006. In outbreak sheep flocks, morbidity was limited, with exceptions for a few flocks. However, almost 50% of the clinically sick sheep died in outbreak sheep herds.     

Phylogenetic analysis of SRLV sequences from an arthritic sheep outbreak demonstrates the introduction of CAEV-like viruses among Spanish sheep

Small ruminant lentiviruses (SRLVs) cause different clinical forms of disease in sheep and goats. So far in Spain, Maedi visna virus-like (MVV-like) sequences have been found in both species, and the arthritic SRLV disease has never been found in sheep until a recent outbreak. Knowing that arthritis is common in goats, it was of interest to determine if the genetic type of the virus involved in the sheep arthritis outbreak was caprine arthritis encephalitis virus-like (CAEV-like) rather than MVV-like. Alignment and phylogenetic analyses on nucleotide and deduced amino acid sequences from SRLV of this outbreak, allowed a B2 genetic subgroup assignment of these SRLV, compatible with a correspondence between the virus genetic type and the disease form. Furthermore, an isolate was obtained from the arthritic outbreak, its full genome was CAEV-like but the pol integrase region was MVV-like. Although its LTR lacked a U3 repeat sequence and had a deletion in the R region, which has been proposed to reduce viral replication rate, its phenotype in sheep skin fibroblast cultures was rapid/high, thus it appeared to have adapted to sheep cells. This outbreak study represents the first report on CAEV-like genetic findings and complete genome analysis among Spanish small ruminants.     

An outbreak of sheep-associated malignant catarrhal fever in bison (Bison bison) after exposure to sheep at a public auction sale.

An outbreak of malignant catarrhal fever (MCF) among bison sold at an auction market was studied for an 18-month period. Forty-five of 163 bison submitted for sale from 8 different bison farms died on 7 other destination farms. The outbreak began on day 50 after the sale, peaked between days 60 and 70, and ended on day 220. Twenty-one dead bison were confirmed to be MCF cases by clinical histories, pathology, and detection of ovine herpesvirus-2 DNA in their tissues with polymerase chain reaction assays. Twenty-four dead bison were classified as suspect MCF cases from clinical histories. No cases of MCF were observed among bison remaining on originating farms or resident bison mixed with sale bison on destination farms. There were no sheep reported within 3 km of originating or destination farms, limiting bison exposure to sheep to the auction facility, where sheep were present for less than 1 day. The outbreak provides an illustration of the temporal distribution of MCF mortality expected in bison and an estimate of the time from exposure until death from MCF after a single short exposure to sheep. The study provides evidence that bison with MCF do not transmit MCF to other bison.     

Detection of wild-type Aujeszky's disease virus by polymerase chain reaction in sheep vaccinated with a modified live vaccine strain

An outbreak of Aujeszky's disease occurred in a flock of sheep which had been housed together with pigs. After the death of five sheep with clinical signs of Aujeszky's disease, the remaining sheep were vaccinated with the Bartha vaccine strain, and the pigs were vaccinated with the 783 vaccine strain of Aujeszky's disease virus. Despite vaccination, however, more sheep died. Brain tissues from four sheep were collected for virus isolation and for immunobistological examinations. Only vaccine virus (gE-negative) was detected in the tissue. After DNA restriction enzyme analysis of the isolated virus, DNA of one or both of the vaccine strains was detected in all sheep. In one sheep field virus DNA was also detected. However, when the polymerase chain reaction was performed on samples prepared from paraffin-embedded tissues, DNA of field virus (gE-positive) was detected in all four sheep. It was probable that the sheep had not yet mounted a sufficient immune response to the vaccine virus, or were already infected with field virus at the time of vaccination. We concluded that the sheep died from field virus infection and not from vaccine virus infection and that only the polymerase chain reaction made it possible to specifically detect even very small amounts of field virus DNA among vaccine virus DNA in all investigated sheep.     

Breeding with resistant rams leads to rapid control of classical scrapie in affected sheep flocks

ABSTRACT: Susceptibility to scrapie, a transmissible spongiform encephalopathy in sheep, is modulated by the genetic make-up of the sheep. Scrapie control policies, based on selecting animals of resistant genotype for breeding, have recently been adopted by the Netherlands and other European countries. Here we assess the effectiveness of a breeding programme based on selecting rams of resistant genotype to obtain outbreak control in classical scrapie-affected sheep flocks under field conditions. In six commercially-run flocks following this breeding strategy, we used genotyping to monitor the genotype distribution, and tonsil biopsies and post-mortem analyses to monitor the occurrence of scrapie infection. The farmers were not informed about the monitoring results until the end of the study period of six years. We used a mathematical model of scrapie transmission to analyze the monitoring data and found that where the breeding scheme was consistently applied, outbreak control was obtained after at most four years. Our results also show that classical scrapie control can be obtained before the frequency of non-resistant animals is reduced to zero in the flock. This suggests that control at the national scale can be obtained without a loss of genetic polymorphisms from any of the sheep breeds.     

An outbreak of bluetongue in sheep in the Sudan

An outbreak of bluetongue and the first isolation of the virus in the Sudan are reported. The disease occurred in sheep stressed by walking for five days when biting arthropods were prevalent. Estimates of the morbidity and mortality rates ranged from about 30 per cent and 2 per cent respectively in adult sheep to around 80 per cent and 100 per cent respectively in lambs. The virus was isolated by the inoculation of suckling mice and embryonated eggs with whole blood from febrile sheep. In a gel precipitation test it reacted with specific antiserum to type 10 BT8 strain. No other agent was isolated. Given the relatively mild nature of bluetongue in indigenous sheep, it is believed that the long walking stress coupled with exposure to sunlight might have aggravated the severity of the disease in this particular outbreak.     

A recent outbreak of rinderpest in East Africa

Rinderpest was brought under control in Kenya in 1976 but in April 1986 an outbreak of the disease occurred in cattle in Western Kenya, five kilometres from the Kenya-Uganda border. This was the first confirmed field outbreak of the disease in Kenya after a lull of over 10 years. Clinical disease was confined to unvaccinated zebu calves aged six to eight months from which rinderpest virus was isolated. High titres of antibodies to rinderpest virus were demonstrated in sera collected from sheep and goats that were grazing together with the affected cattle herds; there was, however, no evidence of clinical disease in these small ruminants and wildlife species in the affected area. The disease outbreak was rapidly stamped out by quarantine and vaccination.     

An outbreak of ringworm in sheep in Ireland caused by Trichophyton verrucosum

An outbreak of ringworm in sheep in Ireland caused by Trichophyton verrucosum is described. The flock consisted of 110 sheep and two separate groups within the flock were affected. Eleven of the first group of 23 sheep and five of the second group of 25 sheep showed lesions. Contact with infected cattle and fomites contaminated by the cattle are believed to have caused the outbreak. An excellent response was obtained in both infected groups by treatment with griseofulvin at a dose rate of 7.5 mg/kg daily for seven days.     

Emory milkvetch (Astragalus emoryanus var emoryanus) poisoning in chicks, sheep, and cattle.

A severe outbreak of Emory milkvetch poisoning in cattle and sheep occurred near Roswell, New Mexico, in the spring of 1975. Mortality averaged 2% to 3% and morbidity averaged 15% to 20%. Emory milkvetch collected from the infested area contained miserotoxin measured as 5 to 9 mg of NO2/g of plant (dry weight). Chicks fed extracts of Emory milkvetch showed toxic signs when fed one dose as 300 mg of NO2/kg of body weight, and died within 5 to 8 hours when fed milkvetch as 400 mg of NO2/kg. A sheep fed Emory milkvetch for 7 days in the form of 38 mg of NO2/kg/day developed signs of nitro poisoning on the 7th day. Cattle were poisoned or died when fed Emory milkvetch as 12 to 20 mg of NO2/ig for several days. The toxic signs observed in the field and under experimental conditions were similar.     

A monoclonal antibody capture ELISA to detect antibody to border disease virus in sheep serum.

An enzyme-linked immunosorbent assay (ELISA) has been developed to detect antibody to border disease virus (BDV) in sheep serum. A monoclonal antibody bound to 96-well microplates was used to capture antigen from detergent-solubilised BDV-infected cells. Single dilutions of test sera were then added to wells containing bound BDV antigen and control wells containing uninfected cell lysates. Specific antibody to BDV was detected by an anti-ovine IgG antiserum conjugated with horseradish peroxidase and the results expressed as ELISA units with reference to a standard curve. Sequential sera from 16 experimentally infected sheep and single sera from 103 sheep involved in a field outbreak were tested in the ELISA and for neutralising antibody. There was good qualitative correlation between the two tests.     

A tremorgenic mycotoxicosis of cattle caused by maize sprouts infested with Aspergillus clavatus

An outbreak of disease affecting a herd of 16 dairy cattle which were fed mouldy, sprouted maize is described. Eight of the cattle were affected, 5 of which died. The clinical signs included muscular tremors, hypersensitivity, ataxia, anorexia and salivation. Aspergillus clavatus was the only fungus isolated from the sprouts. Clinical signs that were indistinguishable from those in the field outbreak were reproduced by dosing the mouldy maize sprouts to a steer and a sheep, and by dosing another sheep with maize inoculated with a pure culture of A. clavatus isolated from the mouldy maize on the farm. Light microscopical examination revealed neuronal degeneration and necrosis in the midbrain, medulla oblongata and spinal cord of all 3 of these animals. The disease is clinically and pathologically indistinguishable from the disease caused by the ingestion of sorghum beer residue, and in certain respects it is similar to toxicoses caused by the ingestion of wheat sprouts and malt sprouts infested with A. clavatus.     

A devastating outbreak of malignant catarrhal fever in a bison feedlot.

In early 2003, an outbreak of malignant catarrhal fever (MCF) occurred in a bison feedlot in southern Idaho. The outbreak resulted in a 51.2% (n = 825) mortality rate among bison, which had been exposed to sheep for 19 days. Diagnosis was made by detection of ovine herpesvirus 2 (sheep-associated MCF virus) DNA in tissues or peripheral blood by polymerase chain reaction (PCR), and by histological examination of tissue lesions. Peak losses occurred between 41 and 55 days postmean exposure time (PME), and reached a maximum of 41 head per day. No known cases of MCF were observed among the 177 head of bison that arrived in the lot 3 1/2 weeks after the departure of the sheep. Of the several thousand head of beef cattle in the lot during the outbreak, only a single case of MCF was identified. This outbreak illustrates the devastating impact the MCF virus can have on bison under certain exposure conditions, the high threat posed by adolescent lambs to susceptible species, the significantly greater susceptibility of bison than beef cattle to MCF, and the lack of horizontal transmission from clinically affected bison to herdmates.     

Abomasal emptying defect of sheep may be an acquired form of dysautonomia

Abomasal emptying defect (AED) is a disease syndrome that primarily affects Suffolk sheep and is characterized by distension and impaction of the abomasum. No histologic lesion has been consistently associated with this condition. There is no known etiology. In this study, nine cases of AED were identified by necropsy, including three rams and six ewes between 2 and 6 years of age. Four of the cases occurred sporadically, and five ewes were submitted on the same day from a single flock. Histologic examination of celiacomesenteric ganglia from six of the affected sheep revealed scattered chromatolytic or necrotic neurons, without inflammation. Chromatolytic neurons were observed more frequently in AED-affected sheep than in seven healthy Suffolk sheep (P < 0.08, weak statistical support). Neuronal necrosis was not observed in any of the healthy sheep. Lineage records of the flock that suffered an outbreak were incompatible with the possibility of a simple inheritance pattern for this disease; furthermore, the very occurrence of AED in outbreak form is inconsistent with transmission solely by inheritance. Only one of the six tested sheep showed concurrent immunohistochemical evidence of scrapie. The lesion pattern in celiacomesenteric ganglia is suggestive of a neurotoxicosis. Neuronal lesions of AED resemble dysautonomic diseases of humans and other animals.     

Dieldrin toxicity in housed Merino sheep

An outbreak of nervous disease with deaths and reproductive failure was investigated in a fully housed flock of 640 super fine wool (Sharlea) Merino sheep. During the 4 months after the flock was dipped in dieldrin, 70 adult sheep died and no live lambs were produced by the ewes. The diagnosis of poisoning with dieldrin was based upon the presence of characteristic clinical signs, pathological findings and the detection of residues of dieldrin in tissues. Deficiency of vitamin A was confirmed in 2 sheep and may have contributed to the reproductive failure.     

Seroepidemiological study of Rift Valley fever (RVF) in animals in Saudi Arabia

Serological prevalence of IgG antibodies against Rift Valley fever (RVFV) virus was investigated in 22 major localities in five different regions of Saudi Arabia where vaccination against RVF virus (RVFV) is not practiced. The study excludes the southwestern region where a major outbreak of RVF occurred in 2000 and where annual vaccination of ruminants is practiced. Sheep and goat IgG-sandwich ELISA were used to test serum samples from sheep and goats, and bovine IgG-sandwich ELISA was used to test cattle sera. A nonspecies-specific, nonantibody isotype-specific ELISA was used to test camel sera. A total of 3,480 sheep, goats, cattle and camels with no previous history of vaccination against RVFV were randomly tested. All tested animals were negative for IgG class antibodies against the virus except four out of 1,508 sheep and three out of 913 goats, which tested positive. All animals were clinically normal and no evidence was found of virus activity in the studied areas. It is, therefore, most likely that those rare positive cases, which constituted 0.002% of the total animals tested, were either false positives or vaccinates smuggled from the outbreak zone. The need for regular monitoring of animals both within the outbreak zone of 2000 and other parts of the kingdom is strongly emphasized.     

Blindness and encephalopathy caused by Helichrysum argyrosphaerum DC. (Compositae) in sheep and cattle.

An outbreak of amaurosis and paresis was observed amongst sheep, and occasionally cattle, which had been grazing on pastures consisting mainly of Helichrysum argyrosphaerum DC. A similar syndrome was produced by feeding the suspect plant to sheep, thereby providing proof if its toxicity. Although none of the sheep became blind and only one developed paralysis, typical sponly lesions were detected in the brains and optic fasciculi of all the experimental animals. The lesion had specific predilection sites, such as the white matter around the lateral ventricles, the optic tracts plus chiasm, the pyramidal tracts and the brachium pontis. Enlargement of the optic fasciculi furthermore gave rise to malacia, papilloedema and retinal changes. Some aged sheep developed cataracts approximately 2-3 months after the initial outbreaks of amaurosis had occurred. Circumstantial and histopathological evidence suggests that the cataracts may be due to chronic Helichrysum poisoning, but this could not confirmed in the present investigation.