November 2010 RVL Monthly Report
A very high proportion of cases investigated by the laboratory service in November involved respiratory disease. Dublin investigated an outbreak of pneumonia in a 100-cow suckler herd where seven weanlings and three fattening heifers had all died suddenly one month after housing. Three weanlings were necropsied and were found to have gross changes consistent with bronchopneumonia. Mannheima haemolytica and BRSV were detected in one of the three animals, Pasteurella multocida and Mannheima haemolytica were isolated from each of the remaining two. Using PCR, Cork confirmed a diagnosis of BRSV infection in the case of a six-month-old calf with broncho-interstitial pneumonia. Four other calves from the same group had died with similar clinical histories. Athlone diagnosed BRSV infection in a nine-month-old weanling with a history of respiratory distress. Although PCR results were inconclusive in this case, the histopathological changes encountered were consistent with BRSV infection.
Post mortem examination of a continental beef heifer which was found dead and submitted to Dublin revealed pulmonary consolidation, serofibrinous pleuritis and pericarditis. Pasteurella multocida, Mannheima haemolytica and Mycoplasma bovis were isolated from the lung while BVD was also detected in tissues. The herd of origin in this case was comprised of bought-in heifers from several different herds; the co-mingling of such animals is likely to have facilitated the spread of such a diverse range of pathogens. Athlone also detected multiple pathogens in the case of a five-month-old weanling with a history of sudden death, Mannheima haemolytica was isolated from the lungs, while PI3 and BVDV were also detected in lung tissue. Limerick detected BVDV in the lung of a two-day-old calf with a history of respiratory distress for 12 hours ante mortem. Pulmonary consolidation was found on gross post mortem examination, and Escherichia coli was isolated from several tissues. A diagnosis of colisepticaemia was recorded. Dublin isolated Pasteurella multocida from the lungs of a continental male weanling which was in poor body condition and had an abomasal ulcer (Figure 1). The role of the abomasal ulcer in ill thrift and development of pneumonia was considered. Dublin also isolated Pasteurella multocida from a nine -month-old Friesian heifer with unilateral bronchopneumonia, hyoproteinaemia and severe oedema of abomasal wall (Figure 2). Oedema may have resulted from loss of oncotic pressure due to the hypoproteinaemia.
Figure 1: Abomasal ulcer in a weanling with poor body condition and pneumonia. Photo: William Byrne.
Figure 2: Severe oedema in the abomasal wall of a nine-month-old heifer with pneumonia and hypoproteinaemia. Photo: William Byrne.
Other respiratory pathogens of cattle found in November included Dictyocaulus viviparous, which caused the death of a five-month-old weanling submitted to Athlone. In a separate case, Athlone necropsied two six-month-old calves with a clinical history of pneumonia and found an abundance of lung worms and thrombi along the pulmonary airways. Coincidental to this, BRSV was also detected in lung tissues, which also showed rubbery consolidation. Athlone necropsied a cow with a history of respiratory distress. Seven other cows from the group were affected with similar clinical signs, and fog fever was confirmed on histopathological examination of tissues.
As well as pneumonia, submissions to the laboratory service in November reflected the diversity of other disease which occurs in cattle in Ireland. Kilkenny necropsied a three-week-old calf with a history of sudden death and bleeding from the navel. The carcass was found to be pale while large amounts of clotted blood were found within the intestine. Testing for BVDV proved negative, and histopathological analysis of bone marrow demonstrated trilineal bone marrow hypoplasia which confirmed a diagnosis of Bovine Neonatal Pancytopaenia (BNP). Athlone necropsied a three-day-old suckler calf and found chalky white deposits on the left ventricular wall. Histopathology revealed myocardial necrosis and mineralisation of lesions, while kidney selenium levels were found to be below the normal range. Nutritional cardiomyopathy (White Muscle Disease) was diagnosed in this case. Athlone also investigated the death of a six-week-old calf with a history of diarrhoea which was refractory to treatment. Abomasal ulceration was found on gross examination of tissues, while hisopathology revealed a proliferative rumenitis with fungal hyphae present at the site of lesions in the abomasum and rumen ¿ a diagnosis of mycotic rumenitis was made.
Limerick diagnosed clostridial myocarditis in a two-week-old calf with a history of sudden death. Lesions indicating fibrinous pericarditis and myocarditis were identified while Clostridium chauveoi was detected at the lesion site using FAT. Sligo reported a number of cases of Blackleg in cattle in November, Sligo also diagnosed Black¿s Disease in an 18 -month-old heifer ¿ the main post mortem finding was hepatic necrosis.
Salmonellosis is always a recurring finding and November proved to be no exception. Dublin diagnosed Salmonella septicaemia in a 10-day-old Belgian blue cross calf, despite that fact that the calf had a satisfactory serum immunoglobulin level, as evidenced by the ZST result. The demonstration of meningitis, interstitial pneumonia and typhoid nodules in the liver on histopathology was consistent with a diagnosis of septicaemia due to Salmonella spp. infection. Limerick isolated Salmonella dublin in tissues from a 10 -month-old weanling with a history of diarrhoea and weakness. Haemorrhagic enteritis was the principal pathological change identified in this case. Kilkenny reported several instances where Salmonella spp. were isolated from faeces submitted for analysis; the presence of fluke eggs was recorded with some of these submissions. Dublin also isolated Salmonella spp. from submitted faecal samples and again like Kilkenny fluke eggs were detected in some cases. In the case of one such submission to Dublin, a number of cows from the submitting herd were affected by profuse bloody diarrhoea; faeces from two cows were submitted and in the case of one sample, Salmonella dublin was isolated, in the case of the other liver fluke eggs were detected. From a separate herd, Salmonella dublin was isolated from faeces submitted to Dublin from a cow with bloody watery diarrhoea, tachycardia and pyrexia. Another diagnosis arrived at from analysis of submitted faecal samples was Johnes disease ¿ Kilkenny isolated Mycobacterium avium subspecies paratuberculosis (Map) from bovine faeces submitted from two separate herds.
Autumn normally sees a seasonal increase in abortion and the high abortion submission rate in November was consistent with this pattern. Dublin reported that the number of abortion cases from which Salmonella spp. were isolated was greater than in recent autumn periods. In one case Dublin investigated an outbreak of abortion in a dairy herd where aborted foetuses ranged in age from early to late gestation. The attending practitioner in this case was suspicious of Salmonella spp. involvement on the basis that aborting cows were febrile, and some were scouring. Salmonella dublin was isolated from submitted foetuses and vaccination of the remaining cow herd was advised. Limerick and Kilkenny also reported a high number of Salmonella-associated abortions. Other abortifacients reported by the laboratories included Arcanobacter pyogenes, Listeria monocytogenes and Aspergillus fumigatus. Athlone necropsied a seven -month-old foetus which had one centrally placed eyed, a ¿bulldog¿ shaped skull, the forebrain was not formed though remaining parts of the brain were normal, there was slight contracture of limb tendons. Holoprosencephaly and cyclopia are usually reported as occurring sporadically. The foetus was seropositive for Neospora caninum.
Cork isolated Actinobacillus pleuropneumonia from the lungs of two pigs with a history of sudden death. Pulmonary consolidation was the principal post mortem finding; Ascaris suum was detected in the small intestine of one of the pigs. Athlone diagnosed erysipelas in a gilt submitted for necropsy. Diffuse lymph node enlargement and pleural petechiation were the main pathological findings, and Erysipelothrix rhusiopathiae was isolated from several organs. Penicillin administration to other affected pigs and vaccination in the face of the disease outbreak was advised.
Sligo reported a number of cases of Pasteurella spp. pneumonia in sheep in November. Sligo also diagnosed clostridial enterotoxaemias on a number of occasions. In another case, clostridial disease was suspected in a lamb with severe pulmonary oedema, there were two other similar mortalities in the flock. Though the lamb had been vaccinated, abscessation was found at the vaccine injection site which raised a doubt as to the efficacy of the vaccine in this case. Limerick necropsied a 19-month- old ram with a history of poor thrive and diarrhoea and while an anthelmintic had been administered, there was no clinical response. Post mortem examination revealed the intestines, both large and small to be filled with copious quantities of watery faeces; Salmonella dublin was isolated on culture of faeces.
Cork diagnosed erysipelas in two 42-week-old chickens submitted for post mortem examination with a history of egg drop and swollen reddened vents. Erysipelothrix rhusiopathiae was isolated from tissues in both cases. Coccidiosis and ascaridiasis were also dconfirmed in both birds. Dublin diagnosed Infectious Laryngotracheitis (ILT) in a hen with a history of an acute episode of respiratory distress and sneezing ante mortem. The hen originated from a backyard flock comprised of 20 hens. Three of these had also died; the outbreak occurred one week after the introduction of a new bird. Post mortem examination revealed catarrhal exudates adherent to the lining of trachea while histological examination of tissues revealed a lymphocytic tracheitis and intranuclear inclusions in respiratory epithelium. PCR results confirmed the diagnosis. Dublin necropsied four fattening turkeys with a history of sudden death, from a flock with a high mortality rate. Serofibrinous peritonitis and pericarditis were evident on post mortem while Escherichia coli was isolated from tissues ¿ mortality rate in the flock dropped back to acceptable levels following antibiotic mediation.
A rabbit presented to Athlone was the fifth to die in the same batch. Histology revealed severe necrotising hepatitis which was consistent with viral haemorrhagic disease of rabbits caused by calicivirus. Cork also diagnosed viral haemorrhagic disease in two rabbits which presented with enlarged livers with white pinpoint foci on gross examination, and periportal hepatic necrosis on histology. In the case of one of the rabbit livers, in addition, numerous parasites consistent with hepatic coccidiosis, presumably Eimeria stiedae, could be seen within the bile ducts in one of the livers (Figure 3).
Figure 3: Photomicrograph demonstrating coccidia in the hepatic bile ducts of a rabbit. Photo: Cosme Sanchez-Miguel.