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RVL Monthly Report May

Bovine

As expected at the time of year, the Regional Veterinary Laboratory service saw a large number of calf submissions in May and, with infectious disease being most prominent, salmonellosis was very prevalent.

Dublin received two homebred Friesian calves from a single herd which had been found dead; one was two-weeks-old, the second four-weeks-old. Both calves were found to be jaundiced on post mortem examination (Figure 1). The older calf had splenomegaly and hepatomegaly, while fibrinonecrotic enteritis was found in the younger calf. Salmonella Dublin was isolated from organs in both cases. Kilkenny isolated Salmonella Dublin from the faeces and enlarged mesenteric lymph nodes of a six-week-old calf with a history of ill thrift and diarrhea. Limerick found diphtheritic enteritis and splenomegaly on necropsy of a six-week-old calf with a history of poor appetite and weight loss, and Salmonella Dublin was isolated from tissues. Kilkenny isolated Salmonella Dublin from the faeces of an eight-week-old calf with diarrhoea and enteritis, which had been out on grass. Other calves from the group of origin were also noted to be scouring at around six weeks of age. Athlone necropsied a calf treated for diphtheria for four days antemortem and found diphtheritic laryngitis, pharyngitis and pulmonary consolidation. Unusually,  Salmonella Dublin was isolated from these lesions. Dublin examined two one-month-old calves which, along with 100 other calves, had been purchased into the submitting herd two weeks previously. One of the two calves had a history of abdominal distension, and the other had watery diarrhoea and weight loss for several days antemortem. Post mortem examination revealed abomasitis and pulmonary consolidation in both calves while one had ascites and the second had enteritis. Salmonella typhimurium was isolated from ascitic fluid in one calf and from intestinal contents in the second. Furthermore, Mannheima haemolytica and Pasteurella multocida were isolated from the lungs in both cases. The transportation and commingling of these 100 calves is likely to have facilitated the spread of these pathogens. Athlone reported isolating both Salmonella Dublin and Mannheima haemolytica from the lungs of a two-month-old calf with chronic suppurative bronchopneumonia, while Kilkenny also reported a number of cases where both Salmonella spp.  and Pasteurella/Mannheimia spp.  were isolated from the same submission. This was usually observed in calves of between two and three months of age. 

Jaundice  

Figure 1: Jaundice in a two-week-old calf with salmonellosis. Photo: William Byrne

A number of cases of Clostridial enterotoxaemia and of malignant oedema in calves were reported by Athlone. Kilkenny diagnosed colisepticaemia and hypogammaglobulinaemia in a three-day-old calf, which had been healthy at birth but then stopped sucking. Sligo saw several young calves with umbilical infections and consequential peritonitis while Athlone isolated Mannheima haemolytica from the lungs of a six-week-old calf which was found recumbent and in respiratory distress, suppurative pleuropneumonia was the main lesion observed on post mortem examination. Limerick diagnosed valvular endocarditis in an eight-month-old Friesian heifer with a history of swollen joints and poor appetite for a number of weeks ante mortem. Staphylococcus aureus was isolated from the cardiac lesions. An 18-month-old feedlot heifer was submitted to Dublin with a history of being found dead, and forelimb lameness had been observed shortly before death. Necropsy revealed interdigital necrobacillosis (“foul in the foot”) in the left forelimb with swelling of the pastern, and further examination revealed a fibrinous pleuritis and peritonitis. Arcanobacterium pyogenes was isolated from inflammatory exudates while PCR testing of spleen confirmed bovine viral diarrhoea (BVD) virus was present. Arcanobacterium pyogenes is one of the pathogens implicated in “foul in the foot” and in this case concurrent immunosuppressive BVD infection may have facilitated the dissemination of this pathogenic agent throughout the body, resulting in polyserositis.   

Viral infections seen in May included several cases of bovine herpesvirus 1 – causing Infectious Bovine Rhinotracheitis (IBR). Kilkenny detected IBR virus in the lungs of a five-month-old calf with pneumonia, while Athlone confirmed IBR infection in a 10-month-old bullock which became aggressive ante mortem, fibrinonecrotic tracheitis was found on post mortem examination. The cause of the aggression was not determined but may have been due to cerebral hypoxia (similar aggression is seen in some cases of babesiosis). Athlone also necropsied a two-month-old calf with a history of abdominal distension and dry faeces antemortem. It was one of two from the same group to have died at the same time. Necropsy in this case revealed pneumonia, abomasal ulceration, diffuse rumenitis with focal necrosis and multifocal necrotising hepatitis, IBR virus was detected in tissues. These findings were consistent with systemic bovine herpesviris 1 infection. 

Kilkenny diagnosed rotaviral enteritis in a three-week-old calf with diarrhoea which suffered from an acute episode of diarrhoea antemortem while Limerick examined a three-week-old calf with a history of dyspnoea and bleeding from the eyes and ears. Widespread eccymotic haemorrhaging on serosal surfaces was found on post mortem examination and while BNP was initially suspected, BVD virus infection was confirmed by PCR testing of tissues.

Parasitic disease diagnosed in May included a case of coccidiosis diagnosed in a calf submitted to Athlone with a history of pining for 48 hours ante mortem. Post mortem examination revealed dehydration, abomasal ulceration and watery blood tinged intestinal contents. The detection of large numbers of oocysts in the  faeces confirmed the diagnosis. Of 877 faecal samples screened for coccidiosis in May, 177 samples yielded a positive result (Table 1). Interpretation of coccidial oocyst burdens is difficult, and can really only be done in conjunction with the history, clinical signs, and post mortem results if available. The absence of oocysts at faecal examination does not rule out coccidiosis because significant clinical disease commonly occurs before oocyst shedding begins. On the other hand the finding of oocysts in faeces (even in extremely high numbers) must be interpreted with caution because the vast majority of coccidia, in both cattle and sheep are non-pathogenic species.

Coccidiosis testing May 2011 (xls 11Kb) 

Table 1: Coccidiosis testing May 2011. Courtesy Alan Johnson

Kilkenny necropsied a stunted emaciated nine-month-old weanling and found partial pulmonary consolidation and a “Moroccan leather” pattern in the abomasal mucosa (this lesion is pathognomonic for ostertagiosis), Pasteurella multocida was isolated from lung lesions while faecal examination detected a strongyle egg count of 21 000 eggs per gram (epg) of faeces, chronic suppurative broncopneumonia and  severe strongylosis were diagnosed. A yearling bovine with a history of pneumonia-like symptoms was submitted to Athlone, and post mortem examination revealed submandibular oedema, hydrothorax, liver enlargement and oedema of abomasal mucosa. The faecal strongyle egg count was extremely high at 45,000 epg and parasitic gastroenteritis was confirmed.

Other diagnoses included a total intestinal obstruction in a two-month-old Charolais calf with a history of depression for a few days antemortem. Post mortem examination revealed a trichobezoar lodged in the terminal ileum with resultant obstruction of outflow to the distal intestine. Athlone saw a six-week-old calf with a history of scour antemortem. Post mortem examination revealed herniation of jejunum into an umbilical hernia and devitalisation of trapped intestine. Kilkenny diagnosed Bovine Neonatal Pancytopaenia (BNP) in two calves from separate herds. One calf was 15 days old, and the other was 18 days old, both were found to have extensive haemorrhage visible on serosal surfaces and bleeding from the nostrils while one had haemorrhagic intestinal contents. BVD-PCR testing of tissues proved negative, while the identification of trilineage hypoplasia in bone marrow using histology confirmed a diagnosis of Neonatal Pancytopaenia. Sligo found peritonitis arising from perforated abomasal ulcers in two calves submitted from the same herd while Kilkenny found perforated abomasal ulceration and peritonitis in two calves from separate herds. One was a seven-week-old calf found dead and the second, a 10-week-old calf, had a history of bloat and constipation. Kilkenny also diagnosed cerebro-cortical necrosis (CCN) in a three-week-old calf, which had a history of “star-gazing”. Limerick diagnosed lead poisoning in a three-month-old calf which suffered a peracute episode of tremors, frothing at the mouth and severe distress antemortem. This was the second calf from the group to have died under these circumstances. A car battery which was found in the environs of the calf accommodation was removed and no further such cases occurred. Cork necropsied a two-month-old calf that showed respiratory distress before death. Post mortem examination revealed a misshapen heart with marked ventricular hypertrophy and a foramen in the upper membranous portion of the interventricular septum (Figure 2). Nutmeg liver and ascites associated with chronic passive congestion were also in evidence; a diagnosis of ventricular septal defect was made.     

Interventricular septal defect  

Figure 2: Large patent interventricular septal defect in a two-month-old calf. Photo: Cosme Sanchez

Ovine & Caprine

The laboratory frequently diagnosed mannheimosis (formerly pasteurellosis) in sheep in May, Dublin examined two lambs from a flock where ten mortalities had occurred. Necropsy of the two submissions revealed suppurative meningitis in one and suppurative pleuropneumonia in the other. Mannheima haemolytica was isolated from both lambs. Athlone necropsied a six-week-old lamb with a history of acute illness ante mortem, and found fibrinous pericarditis on post mortem. Mannheima haemolytica was isolated from tissues. Dublin necropsied a ewe with a history of sudden death where bronchopneumonia and fibrinous pleuritis were identified. Again Mannheima haemolytica was isolated from lesions. Kilkenny encountered a fibrinous pleuritis (Figure 3) on necropsy of an eight-week-old lamb which had died suddenly, bacteriology confirmed mannheimosis/pasteurellosis.

Fibrin  

Figure 3: Fibrin attaching to pleura of eight-week-old lamb with pasteurellosis. Photo: Donal Toolan.

Parasite-associated deaths were frequently reported in May. Sligo investigated a scour outbreak among crossbred ewes in a flock of 300 sheep and found evidence of liver fluke infection among the affected animals.  In a separate case parasitic gastroenteritis was diagnosed in a goat submitted to Sligo with a history of scour. Athlone examined a ten-week-old lamb which was found dead. Peritonitis, multifocal thickening of intestinal mucosa and mesenteric lymphadenopathy were found on necropsy. Histopathology revealed severe enteritis associated with coccidial organisms and testing of faeces confirmed a heavy burden of coccidial oocysts, and acute coccidiosis was diagnosed. Athlone also examined a two-month-old lamb with a history of sudden death. Post mortem examination revealed total blockage of the proximal colon caused by a ball of Moniezia spp.  tapeworms. Many of these parasites were also found along the small intestine, caecal outflow into the colon was completely obstructed. 

Porcine

Dublin identified suppurative meningitis in two weaner pigs submitted from a herd with a history of high mortality in weaners, Streptococcus suis was isolated from lesions. Dublin isolated E coli O149 in the watery faeces of three two-week-old piglets submitted from a herd where there was an outbreak of acute diarrhoea and mortality among suckling pigs. Sligo identified haemorrhage as a result of a bleeding stomach ulcer as the cause of death in a 16-week-old pig.

Equine  

A four-day-old foal with a history of sudden death was submitted to Athlone, this was the fourth foal mortality this year on the same farm. Post mortem examination revealed pulmonary congestion with petechiation and fibrinous pericarditis and while testing for Equine Herpesvirus 1 & 4 proved negative, E coli was isolated from tissues. Neonatal colisepticamemia was diagnosed. Risk factors include contaminated environment or failure of adequate transfer of passive maternal immunity. Sligo isolated Streptococcus dysgalactiae subsp equisimilis from the pneumonic lungs of a six-week-old foal which was found dead. Athlone received a three-year-old horse which was one of five out of a group of six to have died over 24 hours. Evidence suggestive of ingestion of a corrosive substance, such as gastritis and duodenitis, were found on post mortem, and enteric contents were copious and watery. History indicated that bags of iron sulphate used for the treatment of lawn moss were stored adjacent to the horse feed and it was suspected that this was the source of the poisoning.   

Avian

Dublin diagnosed fowl cholera in a mute swan found in a public park, and the isolation of Pasteurella multocida from several organs confirmed the diagnosis. Dublin examined a pigeon submitted from a loft with an outbreak of mortality following acute illness. Watery intestinal contents were found on necropsy of the pigeon, and Salmonella typhimurium was isolated from tissues. Limerick recorded gizzard impaction in hens submitted from two separate flocks, in each case the birds had access to long stemmy grass which was it was suspected contributed to the impactions.