December 2009 RVL Monthly Report
All the RVLs had received substantial numbers of aborted bovine foetuses. A wide variety of pathogens were identified and their frequency is presented in figure 1. Salmonella dublin was the most common cause accounting for 14% of abortions. Grossly visible placentitis was seen in the only case in which a placenta was submitted, emphasising the importance of submitting placenta in addition to a foetus and maternal blood. Dublin diagnosed neosporosis abortion in a 200 cow dairy herd on the basis of histological evidence of non-suppurrative encephalitis and myocarditis in six of ten foetuses aborted within one week.
Figure 1: Prevalence of abortion causing pathogens in bovine foetal submissions between September and December 2009.
Congenital heart defects were diagnosed in a number of calves. Sudden onset recumbency, heavy breathing and lifelessness were consistent features of the history of all. The week old Sligo calf with the atrial septal defect had a pericaridial effusion which the referring veterinary surgeon had noted.
Rotavirus and crytosporidia were the two most common pathogens detected in calf diarrohea samples. Agammaglobulinaemia as a result of insufficient colostral intake was a common predisposing factor. Salmonella dublin was found in a number of calf diarrohea samples submitted to Kilkenny. Salmonella typhimurium was isolated by Dublin from faeces from two calves in a herd suffering an outbreak of calf enteritis. There had been a recent introduction of bought- in heifers to a previously closed herd. Sligo diagnosed cerebellar hypoplasia in a neonatal pedigree Aberdeen Angus embryo transfer calf. The whole cerebrum was replaced by a fluid filled sac and the walls of the cranium were distorted to accommodate it (Figure 2).
Figure 2: Domed skull in calf with cerebellar hypoplasia (photo: Colm O'Muireagain).
Many of the cases of pneumonia submitted to the RVLs had multiple pathogens identified at post mortem. Concurrent hoose infestation in pneumonia cases was recorded by Dublin, Kilkenny and Athlone. Various respiratory viruses were identified in many of these cases, the most common of which was BRSV. Kilkenny found combined respiratory and parasitic problems in many thin or emaciated weanlings. Affected animals were between eight and 12 months of age. The animals necropsied were representative of group cohorts. Large burdens of stomach worms, liver fluke and rumen fluke were found to varying degrees in these cases. Dublin diagnosed suppurative tracheitis and subacute purulent bronchopneumonia in two ten month old beef heifers, from which IBRV and Arcanobacterium pyogenes were detected (figure 3). In this group some animals were showing clinical signs of respiratory disease while others were clinically normal apart from marked pyrexia. Dublin and Athlone diagnosed bronchopneumonia with diffuse emphysema caused by BRSV in a number of eight-month-old calves from different herds.
Figure 3: Suppurative tracheitis in a 10 month old beef heifer (photo: William Byrne).
Diarrhoea and weight loss were consistent features in the histories of the several animals identified with mucosal disease. Oral lesions were noted in a number of cases. Sligo confirmed a recently purchased five year old bull as persistently infected with BVD virus. The bull had started to waste and develop mucosal disease after arrival into the herd.
Kilkenny identified liver fluke in association with Salmonella dublin septicaemia in a three year old cow, with a history of wasting in the two weeks since calving (figure 4). Shallow abomasal ulcers were also identified. Kilkenny found Salmonella Dublin in association with a large fluke and worm burden in an eight month old weanling. Six cohorts had become recumbent and died.
Figure 4: Biliary hyperplasia in a bovine liver chronically infected with fluke (photo: Donal Toolan).
Sligo investigated ill thrift among weanlings and respiratory disease in suckler herd. In analysing weight gain data it emerged that the weanlings from the herd were not performing as well as expected. Parasitology revealed significant liver and rumen fluke burdens in the weanlings. This herd owner was also concerned about respiratory disease among young calves (up to 8 weeks of age). The calves were coughing quite a bit and performance was below par. The calf accommodation was examined and after conducting a smoke test it was concluded there was inadequate outlet space. The bed was damp, thereby contributing to the production of ammonia in an already stuffy shed. Increased outlet space in association with improvements to bedding were recommended, in conjunction with a course of antimicrobial treatment.
Ruminal acidosis was implicated in the deaths of a number of cattle in December. Typically affected animals were dehydrated with abdominal distension. At post mortem there were large amounts of sweet smelling grain rich watery ingesta fermenting in the rumen. One eight month old weanling submitted to Athlone also had a necrotic focus in the liver from which Clostridium septicum was detected. The shortage of fodder combined with the cheap cost of cereals relative to grass silage are possible reasons for increased ab lib concentrate feeding this year.
Paramphistomosis (Rumen fluke) was diagnosed by Athlone, Kilkenny and Sligo in a number of animals during December. Rumen fluke can cause enteritis and poor thrive in growing cattle. Their finding in the rumen at post mortem is the most common diagnostic method although marked hypoalbuminaemia is a regular finding in affected animals.
Continuing the trend of the previous months, acute and chronic fascioliasis were commonly diagnosed in all the RVLs. Indeed Kilkenny reported that there was liver damage in nearly all ovine submissions. Athlone and Kilkenny reported deaths in sheep which had been dosed in the previous months and that the owners were disappointed with continuing losses. The pathology found in these animals was extensive liver fibrosis following severe infestations with immature fluke leading to hepatic insufficiency.
Kilkenny found fluke combining with Salmonella dublin and parasitic gastroenteritis to cause substantial losses on individual farms. Findings at post mortem in such cases included ascites, hydrothorax, liver fibrosis in chronic cases, bilary tract hyperplasia, abdominal blood clots in acute cases, and adult fluke in the gall bladder in chronic cases.
Dublin identified parasitic gastroenteritis in store lambs in a number of flocks. In each flock there was significant mortality and ill thrift. The histories included lethargy, loss of appetite, significant weight loss, weakness and recumbency. Watery diarrhoea and high strongyle egg counts (700 to 3,350 eggs per gram) were observed in these lambs. Lambs from one flock had red watery intestinal contents. Interstitial pneumonia was a complication of the PGE in one lamb.
Athlone investigated an outbreak of coughing, torticollis and a head tilt in a 200 bird turkey flock. On average one of the birds had died every other day over the previous month. Gross PM revealed airsacculitis with pus and inspissated caseous material within the airsacs and a left-sided sinusitis. Although bacteriology was negative, serology of five affected cohorts confirmed avian mycoplasmosis. Avian mycoplasmosis is notifiable. Recovered birds remain infected for life and stress can cause recurrence of disease. Dublin diagnosed Infectious Laryngotracheitis in a 56000 laying hen flock. The problem had initially presented as a drop in production, followed by mortality associated with respiratory signs. A diptheritic membrane was found lining the mucosal surface of the larynx. Histology revealed lympho-histiocytic tracheitis with eosinophilic intra-nucleur inclusions in respiratory epithelial cells
Sligo found a stomach ulcer in a three month old store pig, with melena and anaemia.
Kilkenny made a presumptive diagnosis of Rabbit Haemorrhagic Disease in two rabbits on the basis of periportal necrosis of hepatocytes on histopathology. Kilkenny diagnosed Pasteurella septicaemia in two hares which had a band of fibrin on the lung surface of each.