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January 2011 RVL Monthly Report

Bovine

The laboratory service saw a high number of calf submissions in January. Dublin examined a one-week-old Simmental calf with a history of diarrhoea.  A number of other calves from the same herd had also died under similar circumstances. Necropsy of this calf revealed  suppurative omphalitis and dehydration; rotavirus and Cryptosporidium were detected in faeces. Colisepticaemia was demonstrated on culture of the organs and a low reading on the ZST test was consistent with inadequate immunoglobulin intake. Using ZST testing, Limerick found evidence of inadequate immunoglobulin intake in the case of five calves under one week of age from a single herd where respiratory and enteric disease were serious problems in this age group. Athlone identified hypogammaglobulinaemia in a one-week-old calf which had a history of scour two days ante mortem. Rotavirus was detected in faeces and Salmonella Dublin was isolated from organs. Athlone diagnosed rotavirus infection in two one-week-old calves each from a separate herd, both of which suffered from diarrhoea ante mortem. Kilkenny reported that many faecal samples submitted from scouring calves yielded positive results for rotavirus and Cryptosporidium, while Athlone diagnosed enteric cryptosporidiosis in a 10-day-old Friesian/Holstein calf. Dublin diagnosed Cryptosporidium-associated enteritis in a one-week-old suckler calf that had died within 36 hours of onset of diarrhoea. In a separate case Dublin detected co-infection with both Cryptosporidium and rotavirus in calves submitted from a herd which had a problem with diarrhoea in that particular group.

Other diseases seen in young calves included a defective inter-ventricular septum diagnosed by Athlone in a full term calf that survived for only 15 minutes after parturition. Limerick diagnosed a ventricular septal defect in a neonatal calf which experienced severe acute respiratory distress within hours of parturition. Dublin necropsied a large Charolais bull calf that died 18 hours after birth and found six fractured ribs and extensive intra pulmonary haemorrhage, while Sligo suspected dystocia as common factor in the case of a number of separate submissions of neonatal calves with poorly inflated lungs and scleral haemorrhaging. Dublin necropsied a one-day-old calf and found patchy lobular consolidation of the lungs (Figure 1), white foreign material in the bronchial tree and a copious quantity of milk in the abomasom. Histopathology of lungs in this case revealed foreign material within bronchioles of affected lobules of lung which was consistent with aspiration of milk; aspiration pneumonia was diagnosed.   

Patchwork lobular consolidation  

Figure 1: Patchwork lobular consolidation in the lung of a one-day-old calf with aspiration pneumonia. Photo: William Byrne.

In older calves, bacterial and viral infections were a recurring finding, with infectious respiratory disease being the most common diagnosis. Dublin investigated several separate instances where bought-in store cattle developed respiratory disease several weeks after arriving at their respective holdings. In all of these cases, severe pneumonia was diagnosed post mortem, and in a number of these cases mannheimosis (pasteurellosis) was identified, while in one case Mycoplasma bovis pneumonia was confirmed. Athlone necropsied a six-week-old calf with a history of respiratory distress ante mortem and found severe dehydration, fibrinous pleurisy and diffuse peritonitis. Mannheima haemolytica was isolated from several organs and a diagnosis of septicaemic mannheimosis was made. Sligo diagnosed mannheimosis in the case of a two-month-old calf with a history of poor thrive, lungs were found to be consolidated and Mannheima haemolytica was isolated from affected tissue, biochemical analysis of tissues in this case revealed copper and selenium deficiency. Copper and selenium supplementation of the herd along with Mannheimia/Pasterurella vaccination was recommended.  Kilkenny also diagnosed mannheimosis in a three-month-old calf with a fibrinosuppurative pneumonia and Kilkenny also diagnosed mannheimosis in a yearling calf with a history of sudden death. Pneumonia and fibrinous pericarditis were found on gross examination of the carcass in this case while Mannheima haemolytica was isolated on culture of the lung. There were numerous reports of bovine herpesvirus 1 (BHV1) infection in January. Athlone reported an outbreak of respiratory disease in store cattle in a feedlot, most of which were purchased in the autumn. The outbreak was sudden, affected 20 cattle and caused the deaths of two. One of the two mortalities was submitted for post mortem examination where severe tracheitis and cranioventral pneumonia was found. Testing of tissues yielded a positive result for BHV1, while testing of nasal swabs from affected animals in the group using PCR also proved positive for BHV1.  Athlone also diagnosed infectious bovine rhinotracheitis (IBR) in a six-month-old calf which was found to have severe fibrinonecrotic tracheitis; BHV1 was detected in tissues using PCR. Athlone diagnosed bovine respiratory syncytial virus (BRSV) pneumonia in a number of calves in January, each from a separate herd. These cases included a three-week-old calf, a six-month-old calf and a nine-month-old calf. The diagnoses were often based on histopathological findings which were consistent with BRSV infection.

Other infectious diseases seen in January included a case of salmonellosis in an eight-week-old calf submitted to Limerick, while Athlone isolated Salmonella Dublin from the faeces of a two-month-old calf with a history of weakness and staggering ante mortem. Kilkenny isolated Salmonella Dublin from the faeces of a cow which was pyrexic, dull and depressed. Dublin necropsied three culled beef heifers from the same herd and found arthritis and tenosynovitis affecting several joints in each animal. In the case of two of the three heifers, Mycoplasma spp.  was isolated from fluid harvested from the arthritic joints. Sligo reported seeing several calves with umbilical infections. These frequently progressed to peritonitis and arthritis. Mycobacterium bovis was isolated from the bronchial lymph node of a five-week-old reactor calf which was submitted to Limerick. Mycobacterium bovis was also isolated from the milk of the dam of this calf, which seems likely to have been the source of infection.   Limerick diagnosed bovine viral diarrhoea virus (BVDV) infection on a number of occasions. BVDV antigen was detected in a newborn calf which died two hours after parturition and in an eight-week-old calf with diffuse peritonitis. This latter calf originated from a group of calves, six of which were found to have BVDV antigen in their serum. Limerick also identified BVDV infection in an eight-month-old weanling with a history of profuse watery diarrhoea for five days ante mortem. Testing of serum submitted to Kilkenny from two scouring weanlings yielded a positive result for BVDV antigen, and two other weanlings from the same herd had died the week before after an episode of scouring.      

Other interesting cases seen in January included a 14-month-old bull submitted to Athlone which was found dead without any clinical signs having being observed ante mortem. Diffuse peritonitis and a perforating abomasal ulcer were found on gross examination of the carcass. The ulcer was a long-standing lesion and was considered to have perforated shortly before death.  Athlone also investigated the death of a ten-year-old Charolais bull with a history of a stiff gait which progressed over several months to ataxia. Clinical signs were first noticed at three months of age, and a half-sister of this bull had also developed similar clinical signs. Histopathology revealed eosinophilic plaques in the white matter of the brain (Figure 2) and spinal cord   and on the basis of these findings a diagnosis of Progressive Ataxia of Charolais Cattle was made. This well recognised  condition is is seen in a familial pattern, but the mode of inheritance is not understood. 

Eosinophilic plaques  

Figure 2: Eosinophilic plaques (arrows) in the white matter of the brain of a ten year old Charolais bull diagnosed with Progressive Ataxia of Charolais Cattle. Photo: Jim O'Donovan.

Bovine abortion

Athlone reported a 69% rise in the number of aborted bovine foetuses submitted in January 2011 over the number submitted in January 2010. Arcanobacterium pyogenes, Salmonella Dublin, BVDV and Listeria monocytogenes infections were the most common diagnoses made. Dublin investigated several submissions of bovine abortion in January. Salmonella spp. and Listeria monocytogenes were the most common abortifacients identified, while Kilkenny reported Salmonella Dublin and Arcanobacterium  pyogenes as the bovine abortifacients most usually diagnosed in January.

Ovine

Athlone necropsied a four-day-old lamb, the eighth lamb to die in the flock of origin. All of the affected lambs became dehydrated from two days of age, while yellow faecal staining was found on the perineum and hindlimbs. E. coli K99 infection was identified on examination of faecal samples and vaccination against E. coli K99 was recommended. Sligo diagnosed hepatic encephalopathy in a mountain lamb – this condition has been associated with cobalt deficiency in Scottish flocks.

Dublin received two cases (one ewe and one ram) each from a separate flock, of single pulmonary abscessation. Ante mortem, the ram became recumbent without responding to treatment while the ewes which had a larger abscess was found dead. In both cases there was evidence of prior liver fluke infection though current liver fluke infection was not detected. Sligo necropsied a four-year-old ewe which was found dead away from the flock. The uterus contained two autolytic lambs and a large volume of necrotic tissue and fluid. Acinetobacter wolffii was isolated from the uterus; this is an environmental organism which can become an opportunistic pathogen. A diagnosis of septicaemia due to septic endometritis was made in this case. Sligo also saw a case of chronic fibrino-purulent pleurisy and pyothorax in a three-year-old ewe (Figure 3) with a history of progressive dyspnoea. Aerococcus viridians was isolated from the foul smelling pus in the pleural cavity. Kilkenny diagnosed ovine pulmonary adenomatosis (Jaagsiekte) in a ewe which was found dead. Necropsy revealed pale nodules scattered within the lung parenchyma, and histological examination of these nodules confirmed Jaagsiekte. However Salmonella typhimurium was also isolated from tissues and this was considered the cause of death given that Jaagsiekte is a chronic condition. Sligo diagnosed cystic pyelonephritis in a four-year-old ewe with a history of ill-thrift and inanition. On necropsy the right kidney was found to be enlarged, and the renal pelvis was filled with brown pus which was packed with coliform bacteria.

Copious pus  

Figure 3: Copious accumulation of pus (arrow) in the pleural cavity of a three-year old ewe with chronic fibrinopurulent pleurisy and pyothorax. Photo: Colm O Muireagain.

Ovine abortion

Athlone reported several submissions of ovine abortion in January. Chlamydophila abortus was the most commonly diagnosed abortifacient in aborted ovine foetuses examined in Athlone, while ovine abortions caused by Toxoplasma gondii and Arcanobacterium pyogenes were also encountered. Kilkenny isolated Campylobacter fetus fetus from a number of submitted aborted lambs, while Toxoplasma gondii was also diagnosed as a cause of ovine abortion in Kilkenny.

Porcine

Dublin detected Escherichia coli serotype O138 in faeces samples from diarrhoeic piglets that had died suddenly after onset of diarrhoea.

Porcine nasal swabs submitted to Dublin from an integrated pig herd in which pigs were transiently inappetent, depressed and coughing for less than five days yielded a positive result for Swine Influenza virus (H1N1), when tested by Virology Division CVRL Backweston.