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December 2010 RVL Monthly Report

Bovine

Pneumonia was a very common finding in December. Athlone necropsied a yearling heifer with a history of coughing and found cranioventral consolidation of lungs on gross examination of the carcass. Histology revealed a subacute fibrinosuppurative bronchopneumonia, and a presumptive diagnosis of pasteurellosis was made based on pathological findings. Dublin investigated the death of an eight-month-old calf which was imported into a herd as one of a group of store cattle, several of which subsequently died. Post mortem examination of the calf revealed a severe pleuropneumonia. Histology confirmed an acute fibrinosuppurative  pleuropneumonia and although no pathogens were isolated on culture, due perhaps to ante-mortem antibiotic use, a presumptive diagnosis of Mannheima haemolytica  shipping fever was made based on pathological findings.  Sligo also diagnosed Mannheima haemolytica pneumonia in the case of several bovine submissions in December while Sligo also diagnosed Bovine Respiratory Syncytial Virus (BRSV) in two calves submitted from a single outbreak of pneumonia. Poor ventilation and overcrowding in the calf accommodation was implicated as a contributing factor in this particular disease outbreak. Limerick necropsied two weanlings submitted from the same herd, both having a similar history of ill thrift and respiratory distress. BRSV was detected in the lungs of one of the two weanlings and evidence of lungworm infection was found in the second. Dublin examined a three-month-old Charolais calf which died following an episode of respiratory distress. Gross examination of the calf revealed cranioventral consolidation of the lungs with fibrin tags on pleural surfaces, while histological examination of the lungs revealed changes consistent with BRSV infection. PCR testing of lung tissue yielded a positive result for BRSV, confirming the diagnosis. In a separate case, Dublin investigated an outbreak of respiratory disease on a large beef-finishing unit. Cattle were bought in during the autumn and maintained in slatted sheds or open barns. Following the severe cold weather in early December, many animals developed clinical signs suggestive of Infectious Bovine Rhinotracheitis (IBR) and four cattle that died were submitted to the laboratory for post mortem examination. All four carcases presented with severe necrohaemorrhagic laryngotracheitis (Figure 1), and Infectious Bovine Rhinotracheitis (IBR/bovine herpesvirus 1) virus was detected by PCR in tissues in all four cases. 

Necrohaemorrhagic laryngotracheitis  

Figure 1: Marked necrohaemorrhagic laryngotracheitis in a bovine infected with infectious bovine rhinotracheitis (bovine herpesvirus 1). Photo: Eoin Ryan 

Unsurprisingly salmonellosis featured prominently among the diagnoses in December. Athlone necropsied a two-week-old calf which was depressed for one week ante-mortem. The main pathological finding was severe dehydration of the carcass, and isolation of Salmonella Dublin from several tissues confirmed the diagnosis of Salmonellosis. Dublin necropsied a four-month-old bucket fed Friesian calf which was scouring for 36 hours ante-mortem. Five other calves from the group died under similar circumstances over a period of two weeks. Gross examination of the carcass revealed watery intestinal contents, while histology revealed multifocal necrotising hepatitis; the isolation of Salmonella Dublin from several organs confirmed a diagnosis of salmonellosis.

Bovine Viral Diarrhoea Virus (BVDV) was detected in the tissues of a weanling submitted to Athlone. This calf also presented with a diffuse pneumonia on necropsy and Mannheima haemolytica was isolated from the lung. Kilkenny confirmed BVDV infection in a 2-year-old heifer with a history of diarrhoea and emaciation, while BVDV was detected in tissues in a fifteen-month-old heifer submitted to Limerick with a history of ill thrift and diarrhoea. Athlone investigated the cause of chronic diarrhoea in a three-week-old calf which was scouring from a few days after birth. The calf was emaciated and dehydrated on presentation to the laboratory while on necropsy the main finding was watery colonic contents; rotavirus was detected in these colonic contents.

Other cases seen in December included caudal vena caval thrombosis in a six-year-old cow submitted to Sligo. This cow had a history of epistaxis for three days ante-mortem and post mortem examination revealed thrombosis in the caudal vena cava, while pulmonary abscessation was also evident. Cork diagnosed cutaneous lymphoma in a two-year-old bullock with numerous widely distributed large flattened cutaneous masses, some of which were bleeding heavily, secondary to trauma (Figure 2).  Histological examination of the skin lesion revealed a large infiltration of lymphoid cells throughout the dermis, epidermis and subcutaneous tissues. As a precautionary measure the animal was tested for Enzootic Bovine Leukosis (EBL) and a negative result was obtained. Cork also suspected Bovine Neonatal Pancytopaenia (BNP) in the case of three calves from three separate herds. Pathological and epidemiological findings were suggestive of BNP, but histological confirmation of BNP is pending. Sligo investigated the death of a neonate which died four hours after parturition and found four broken ribs, partial aeration of lungs and haemorrhage into the thoracic cavity. These changes were indicative of trauma such as being stood on by the dam. Kilkenny examined a hock joint from a 10-year-old cow which suffered from chronic lameness which was unresponsive to antibiotic therapy. Post mortem examination of the joint revealed articular cartilage degeneration, with thickening of the joint capsule. Mycoplasma bovis was isolated from the joint fluid. Dublin necropsied a four-day-old Charolais calf which had a poor suck reflex at birth and became progressively depressed ante mortem. Segmental aplasia of the colon (atresia coli) was identified on post mortem.    

Cutaneous lymphoma  

Figure 2: Two year old bullock with cutaneous lymphoma and severe haemorrhage evident from the lesions. Photo: Cosme Sanchez.

Bovine abortion

The laboratory service saw a typical seasonal increase in the number of abortion cases it was presented with in December. Athlone diagnosed Salmonella Dublin infection from two separate cases of bovine abortion, and in another case Athlone isolated Campylobacter spp.  from foetal stomach contents. Kilkenny also isolated Campylobacter spp.  from the abomasal contents of two seven-month-old foetuses, each from a separate herd. Suppurative pneumonia was seen in one of these two foetuses, while peritonitis was found in the other. Campylobacter spp.  is recognised as a cause of sporadic abortion in cattle; multiple cases are exceptional. Kilkenny reported that Salmonella spp.  was the most common abortifacient isolated from submitted foetuses.  Arcanobacterium pyogenes, Bacillus licheniformis and Listeria monocytogenes were also isolated from foetal submissions to Kilkenny. In the case of the Salmonella-associated abortions, Kilkenny reported that in many cases there was advanced post mortem change evident in the foetus (Figure 3) with a very strong smell of decomposition. Dublin dealt with several cases of abortion in December. Causal agents identified included Salmonella Dublin, BVDV, Listeria monocytogenes and Arcanobacterium pyogenes. Sligo necropsied a calf with hydrocephalus (Figure 4) which was delivered by caesarean section. The cranium of this calf was grossly distended with serosanguinous fluid and a tiny rudimentary brain was found. The calf was a twin and the large head prevented the dam giving birth to either calf.

Post mortem gas in lungs  

Figure 3: Post mortem gas formation in the lungs of a seven months gestation bovine foetus infected with Salmonella Dublin is particularly marked in the interlobular septae. Photo: Donal Toolan.

Severe hydrocephalus  

Figure 4: This newborn calf with severe hydrocephalus had to be delivered by caesarian section. Photo: Damien Barrett.

Ovine and Caprine

Sligo diagnosed Johne’s disease in a four-year-old ewe which had been scouring for a week. Granulomatous enteritis was confirmed on histological examination of tissues, while acid fast bacilli were also detected on Ziehl-Nielsen stained smears of intestinal mucosa. Athlone necropsied a three-year-old goat which was submitted from a group where four other goats had died over the previous three weeks. Gross examination of the goat revealed blood stained colonic contents with sloughing of the mucosal lining. Parasitological examination of faeces revealed a severe burden of coccidia.

Ovine abortion

Athlone diagnosed Chlamydophila abortus infection in aborted twin foetuses. “Chlamydia Clearview” testing of coat swabs yielded a positive result while a diagnosis of Ovine Enzootic Abortion was further supported in this case when screening of maternal serum revealed antibodies specific for Chlamydophila abortus. Kilkenny isolated Salmonella Dublin from the abomasal contents of aborted twin lambs.

Pigs

Athlone investigated the sudden deaths of two suckling pigs from the same management group, and found marked pericarditis on post mortem examination. Streptococcus suis was isolated from multiple tissues in both carcasses, confirming a diagnosis of streptococcal septicaemia in this case.

Avian

Dublin necropsied an adult hen with a history of ill thrift and inappetence for a number of days ante mortem. The hen originated from a small backyard flock, and three other members of the flock had died in similar circumstances. Post mortem examination revealed multiple pale nodular lesions located within the intestinal wall or adherent to intestinal serosa, while histological examination of these nodules revealed them to be comprised of encapsulated granulomata. Though avian TB was initially considered, the histological lesions did not conform the classic TB granuloma presentation and also, testing of tissues for Mycobacterium spp.  yielded a negative result. Histology in this case also revealed severe coccidiosis with abundant coccidian organisms associated with the granulomata. Coccidial oocysts were detected in faeces and a diagnosis of diffuse nodular coccidiosis was indicated.

Cork diagnosed erysipelas in a chicken submitted from a flock with reduced egg production.  Some of the birds, including the submitted chicken, had reddened and swollen vents. Isolation of Erysipelothrix rhusiopathiae from the lungs confirmed the diagnosis. Cork necropsied a one-year-old hen with a history of respiratory distress ante mortem, PCR testing of pulmonary tissue yielded a positive result for both Infectious Bronchitis (IB) and Infectious Laryngotracheitis (ILT).