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August 2010 RVL Monthly Report

Bovine

Hoose pneumonia was a common finding in carcasses submitted to the Regional Veterinary Laboratories during August. Kilkenny diagnosed hoose pneumonia in a four-month-old calf that on post mortem was found to have lungworms in the trachea and bronchi while Kilkenny also diagnosed hoose pneumonia in a three-year-old cow that had a heavy lungworm burden in pulmonary airways (Figure 1). Limerick diagnosed hoose pneumonia in a four-month-old calf that had a history of respiratory distress while Dublin diagnosed severe lungworm infection a six-month-old heifer with a history of acute pneumonia. Athlone diagnosed lungworm infection in a five-month-old calf. In this case the lungs had a rubbery texture on post mortem examination and many lungworms were found in the trachea and bronchi.

Lungworm in bronchial tree

Figure 1: Lungworm infestation of the bronchial tree in a three-year-old cow. Photo: Donal Toolan.

Pneumonias of other aetiologies included a case of two calves, one two months of age, and the second six months of age, submitted from the same premises to Kilkenny; both had pneumonia and were both infected with Histophilus somnus. Kilkenny also confirmed IBR virus in samples from an 11-month-old animal with severe tracheitis. Athlone necropsied two calves from a herd that had multiple mortalities over the summer. The predominant clinical sign was coughing.  Both calves were found to have a necrotising pleuropneumonia and both Pasteurella multocida and Salmonella dublin were isolated from one of the calves. Dublin examined a weanling bullock from a farm that bought stores for fattening. Recently bought-in animals were suffering from ill thrift. Necropsy of the submitted animal revealed bronchopneumonia, fibrinous pleuritis, watery diarrhoea and inflamed abomasal mucosa. Pasteurella multocida was isolated from the lung and a heavy strongyle egg burden was detected in faeces. A diagnosis of pneumonic pasteurellosis and parasitic gastroenteritis was made.

Dublin investigated an outbreak of severe scour in a group of 50 eighteen-month-old heifers.  Three mortalities were recorded in this outbreak and Dublin examined two of the three fatalities.  In both there was evidence of dehydration and diarrhoea and diffuse haemorrhagic abomasitis was also evident (Figure 2). Ostertagia spp. nematodes were observed in the abomasal mucosa on histopathology. A diagnosis of acute severe parasitic gastroenteritis in dairy heifers in their second grazing season was made. The farm had used pulse-released anthelminthics in all calves and yearlings at turnout in previous years but this dosing regime was discontinued the year the outbreak took place. It seems likely that this practice impaired the acquisition of immunity to parasitic worms in these animals as calves the previous year.

Inflammation of abomasal mucosa

Figure 2: Severe diffuse inflammation of the abomasal mucosa in a yearling bovine. Photo: William Byrne.

Kilkenny reported several cases of salmonellosis in cows during August. The histories of these cases were similar and included watery or bloody diarrhoea, high fever and milk drop.  Salmonella dublin was isolated in all of these cases, but many also had concurrent liver fluke infestation. Athlone diagnosed salmonellosis in a 29-month-old Charolais bullock, while fasciolosis was also found in the same animal. Dublin investigated a severe scour and weight loss problem in a group of five dairy cows. Faeces collected from affected animals in the cohort yielded both Salmonella dublin and liver fluke eggs when analysed. Such concurrent infection with liver fluke and Salmonella dublin has been widely reported in the literature and a synergistic relationship between the two pathogens has been postulated.

Sligo reported an increase in babesiosis in August, while Limerick diagnosed babesiosis in a two-year-old bullock with signs of haemoglobinuria. The diagnosis was made when giemsa staining of a blood smear from this animal revealed red blood cell inclusions characteristic of Babesia spp.

Sligo diagnosed a BVDV viraemia with widespread haemorrhage in a three-month-old calf presented with acute dullness, haematuria and melaena with frank blood clots. The carcass appeared anaemic and dehydrated and there were multifocal randomly distributed ecchymoses and petechiations throughout. Haemopericardium and intra-articular haemorrhage were also evident while gall bladder contents were bloodstained. Detection of BVDV antigen in serum confirmed the diagnosis in this case. Kilkenny detected BVDV antigen in serum submitted from a two-year-old heifer with acute severe diarrhoea, while Kilkenny also confirmed BVDV infection in the case of a calf with chronic diarrhoea and ill thrift.  

Athlone diagnosed two cases of blackleg from each of two separate herds; one was in a six-month-old weanling and the other in a two-year-old bullock. The history given in each case was of `sudden death¿. Kilkenny suspected blackleg as the cause of death in the case of two animals, each from a different herd. Limerick suspected botulism as a cause of death in the case of a two-year-old Friesian heifer with a history of paralysis which was first observed 12 hours ante mortem. This was the fourth such case that occurred in the herd since May. Though the farm was adjacent to a broiler unit, a search of the land for a possible source of toxin was unsuccessful.

Lead poisoning was diagnosed in two calves submitted to Athlone. These calves originated from the same group and had been moved to new ground approximately a week ante mortem. Toxic levels of lead were detected in the renal cortex of both animals. Limerick necropsied a six-month-old calf with a history of blindness, depression, inappetence followed by recumbency and death. The interval between onset of illness and death was less than 24 hours and this calf was the third such mortality in the group in as many weeks. Toxic levels of lead were found in the renal cortex and the herdowner was advised to move this group of animals to alternative pasture without delay, pending identification and removal of the source. 

Other interesting cases seen by the laboratory service included a nine-year-old cow submitted to Limerick that was reported to have become stiff hours before being found dead. Acute severe summer mastitis was diagnosed. Kilkenny diagnosed abomasal ulceration in a cow that was found dead with no history of clinical illness (Figure 3). Large blood clots were found in the abomasum indicating that death was due to acute haemorrhage from the ulcer. Athlone diagnosed suppurative encephalitis in a two-year-old heifer with a history of blindness and depression for two days ante mortem.  he histological changes in the brain were consistent with listeriosis.  Athlone also diagnosed cerebro-cortical necrosis (CCN) in a six-month-old calf that had a history of blindness, recumbency and inappetence.

Focal ulceration of abomasal mucosa

Figure 3: Focal ulceration of the abomasal mucosa in a four-year-old cow. Photo: Donal Toolan.

In the case of younger bovines, Kilkenny diagnosed rotavirus enteritis in a one-month-old calf, and a four-month-old calf submitted for post mortem was found to have bilateral necrotic laryngitis with suppuration in the necrotic cartilage and narrowing of the laryngeal opening. Calf diphtheria was diagnosed. Limerick diagnosed an atrial septal defect in the heart of a two-day-old calf that had a history of weakness and recumbency since birth. 

Kilkenny isolated Salmonella dublin from a number of aborted bovine foetuses while Dublin also isolated Salmonella dublin from a foetus that was submitted from a dairy herd that had reported multiple abortions in the recent past. Athlone examined a foetus, which was aborted by a cow that subsequently died from septicaemia. Arcanobacterium pyogenes was isolated from the foetus, and it was suspected that the foetal infection might have been linked to the maternal septicaemia.

Ovine

Kilkenny investigated mortality in a group of lambs aged four months. Six out of the group had died over a period of a week with a clinical history of inappetence and jaundice for two or three days ante mortem (Figure 4). One of the affected lambs was submitted for post mortem examination and was found to have haemoglobinuria and to be severely jaundiced.  Hepatic and renal tissue copper levels were found to be at toxic levels.

Scleral icterus in lamb

Figure 4: Scleral icterus (jaundice) in a four-month-old lamb with copper poisoning. Photo: Donal Toolan.

Porcine

Dublin necropsied two sixteen-week-old pigs that had a clinical history of nervous signs and depression.  Histopathological examination of the brains of both pigs revealed a laminar cortical necrosis that is typical of salt poisoning/water intoxication. 

Avian

Three hens were submitted to Limerick from a backyard flock with a history of poor egg production, depression and peri-orbital swelling. Serological screening of blood samples collected from the birds ante mortem revealed significant titres to Mycoplasma gallisepticum. Kilkenny diagnosed colisepticaemia in a group of three turkey poults aged approximately four days old while Athlone isolated Salmonella typhimurium from several organs in the case of two geese with a history of inco-ordination. In a separate case, Athlone necropsied a broiler with a history of melaena and apparent abdominal pain. Haemorrhagic intestinal contents were found on gross post mortem examination, while histopathology revealed a heavy coccidial infection. Dublin investigated a mortality problem in a group of six-week-old chicks that were dying within a week of having arrived into new pens. Post mortem examination of submitted birds revealed matted fibrous matter and pine needles in their gizzards but there was no evidence of any food material in their crops, while coccidial oocysts were found in faeces. The flock owner was advised to discontinue feeding birds from the floor surface and to feed the birds from trays.