FOOD/FARMED ANIMALS

Acute respiratory aspergillosis in commercialducklingsDaniel Parker, Andrew Walker

Slate Hall Veterinary Practice,Cambridge, CambridgeshireCB24 8QG, UK

Correspondence toAndrew Walker,andrew@slatehall.co.uk

Received 22 October 2013Revised 17 November 2013Accepted 16 December 2013

To cite: Parker D, Walker A.Vet Rec Case Rep Publishedonline: [please include DayMonth Year] doi:10.1136/vetreccr-2013-000024

SUMMARYSudden onset high mortality was reported in eight-day-old Pekin ducklings. Initial investigations failed toconfirm a definitive diagnosis due to the lack of grosspathological signs and limited microbiological screeningof postmortem samples. Poor quality top-up beddingwas the likely source of the Aspergillus infection, andfinal mortalities of the flocks were 60 per cent and 52per cent. Investigation into high-mortality episodes inducklings should include microbiological screening forfungal infections even if there are no clinical signs orgross pathological signs on postmortem examinationsuggestive of Aspergillus. Bedding should be routinelyscreened for Aspergillus contamination prior to use inneonatal ducklings.

BACKGROUNDAspergillosis is fortunately a rare occurrence inmodern poultry production in the UK.Aspergillosis is known colloquially as ‘brooderpneumonia’ as it was most commonly diagnosed inneonatal poultry associated with infection ataround hatching. In the past, hatching eggs weremore susceptible to contamination with Aspergillusspores because manual nest boxes in breederhouses were bedded with wood shavings, ryegrassor straw. Most breeder houses in the UK are nowequipped with automated nest boxes with‘Astroturf ’ replacing conventional materials as nestliners. Astroturf bedding is less likely to be con-taminated with aspergillosis spores than the con-ventional bedding materials. The case is alsoimportant because the acute nature of the mortalityresulted in few gross pathological lesions, makingan early diagnosis difficult. Finally, both the initiallaboratory investigation and the second laboratoryinvestigation did not use specific fungal culturetechniques in the diagnostic panel, and we wouldrecommend that specific fungal culture plates beused in future in episodes of acute mortality inbrooding poultry.

CASE PRESENTATIONHigh mortality with a sudden onset was seen ineight-day-old ducklings. The ducklings were afast-growing Pekin strain. The farm consisted ofthree sheds, although house 1 was not in use dueto renovation. Sheds 2 and 3 were identical indimension and internal lay out. Both sheds werenaturally ventilated, the ducklings being broodedunder gas-fired canopy brooders.In total, 9200 ducklings were placed into house

2 and 8764 ducklings were placed into house 3. All

the ducklings were sourced from the same hatcheryand the same parent flock, which was 36 weeks oldwhen the eggs were laid. The egg age prior tosetting was five days. The eggs had been set on thesame day; however, the spread of hatch wasextended, so the hatchery manager decided to‘take-off ’ the hatched ducklings and return theunhatched eggs to incubator. The first hatchedducklings were placed into shed 2, and then24 hours later the late hatched ducklings weretaken off and placed into shed 3.

INVESTIGATIONSDay 8A sample of dead birds from the older birds on sitewas submitted to the practice laboratory on theafternoon of day 8 because of a sudden increase inmortality during the previous 24 hours. The birdswere reported to be dying suddenly with no sick orlethargic birds noted. The dead ducks were foundmainly in a ventral recumbence with the head andneck stretched out in front. Postmortem examin-ation revealed the following:The birds examined were all well below thetarget weight of 280 g at eight days 8 enlargedlivers with some congestion and reddening,7 enlarged spleens,9 lung congestion,5 mild gizzard ulceration,5 chronic yolk sac infections,1 peritonitis associated with a chronic yolk sacinfection,1 bacterial septicaemia,1 nephritis,2 mild tibial dyschondroplasia.No lesions were observed in the air sacs of these

birds.Swabs collected from liver and yolk sac were

plated onto Sheep’s Blood and MacConkey agarand cultured at 37°C for 24 hours. Moderategrowths of Staphylococcus and Escherichia colispecies were isolated from liver samples and mod-erate growths of Staphylococcus and Streptococcuswere isolated from yolk sac samples.The gizzards of all the ducklings contained feed

but also contained excessive amounts of fibrousmaterial, indicating that the ducklings were eatingthe straw litter. The mild gizzard erosions wereprobably the result of abrasion due to litter eatingas there was no obvious gross inflammation presentbeneath the gizzard cuticle. Subjectively, the tibiaand metatarsal bones and beaks appeared to be softand malleable in the birds submitted for post-mortem examination; two also had early tibial

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dyschondroplasia lesions. Tibial dyschondroplasia and wideningof tibial growth plates is not in our experience an uncommonfinding in fast-growing strains of Pekin ducks.

Pulmonary congestion and pulmonary hyperaemia werepresent in the dead birds. Although there was some hepatic andsplenic enlargement, the carcasses did not have a typical septi-caemic appearance and the bacterial growths on culture werenot profuse enough to suspect a bacterial septicaemia.

No firm diagnosis was made on this submission.

Day 9The daily mortality rate in shed 2 had continued to increase onthe morning of day 9. Furthermore, the daily mortality rate wasrising in the younger birds in shed 3. A site visit wasundertaken.

The ducklings were evenly distributed in the brooding area ofthe shed. The ducklings were less active than expected but didrespond with increased activity when the shed was walked. Theducklings had been bedded down by the farm staff, as wasstandard practice, two hours before the site visit. A number ofducklings died suddenly during the site visit.

The air quality in the sheds appeared ‘stuffy’ although therewas no obvious smell of ammonia or excessive dust. The largesquare straw bales in the centre of the sheds were visually ofpoor quality with an obvious musty smell to them.

Eight gas canopy brooders were present in each shed. Thecompany target temperature by day 8 was 21°C. The ambienttemperature within both houses was 22–23°C. Ventilation wasmanaged manually with the inlets and outlets opened initially atday 3 and adjusted as required. At the time of the site visit, theair inlets were opened fully as the atmosphere in the shed was‘stuffy’ and there was a suspicion of carbon monoxide poison-ing. The ventilation inlets were opened fully for approximately30 minutes to allow a complete change of air within the sheds.The ducklings initially appeared to respond well to thisincreased ventilation with increased activity. However, increas-ing the ventilation rate resulted in too greater drop in shed tem-perature determined by the ducklings starting to ‘clump’ underthe gas brooders.

It was advised at the time of the visit to re-bed using freshstraw bales of better quality from outside the brooding environ-ment with a minimum depth of 6 inches to reduce the risk ofany mycotoxin or toxin that might have been present in thebedding. It was also advised to change the feed as this may havebeen a potential source of a mycotoxin.

Due to the inconclusive findings at this stage, a sample ofdead ducklings from shed 3 was submitted to the local AnimalHealth and Veterinary Laboratories Agency (AHVLA) labora-tory. A notifiable disease was considered as a possible cause ofthe persistent high mortality but was not suspected at this stageon the basis of the clinical findings and postmortem examin-ation. Notifiable diseases were discussed with the AHVLA at thetime of submission, but no formal investigation was instigated.

Interim postmortem findings by the AHVLAwere as follows:Skin and subcutis: Subcutaneous tissues were slightly dry.Musculoskeletal system: Tibial growth plates were quite widein all 10 birds.Peritoneal cavity: The livers were dark. A persistent green dis-coloured yolk sac was present in one bird.Alimentary system: There was no or minimal food in the giz-zards, some contained fibrous material (likely beddingmaterial).Respiratory system: Mucus was present at the nares of severalducklings when pressure was applied to the beak, no mucus

was present in sinuses and some mucus were present in theoropharynx. Approximately six of the ducklings had darkpurpling of the ventral parts of the lungs. One bird had 1–2 mm multifocal white nodules throughout the lung substancethat was firm. No lesions were observed in the air sacs of thebirds presented.Lymphoreticular system: The spleens were not enlarged butthere was blotchy reddening of the spleens.Microscopy: No significant organisms were detected in wetpreparations from the duodenum, mid-intestine and caecum.Bacteriology: Sparse growths of non-haemolytic coliform bac-teria were isolated from lung and liver. Sparse growths ofα-haemolytic streptococci were isolated from liver and lung,with sparse growths of non-haemolytic staphylococci isolatedfrom spleen and lung.Yolk sac, liver, lung and brain: No bacterial growth.Intestines: Profuse growths of non-haemolytic coliform bac-teria were isolated with a few α-haemolytic streptococci.

Day 10A further visit to the farm was made to reassess the environmentas the mortality rate had not reduced over the preceding 24 hours.

Twenty-five ducklings presented in recumbancy and weregasping. Although the flock’s general demeanour had improved,there were still a significant number of lethargic birds. Furtherpostmortem examinations were carried out upon dead and leth-argic birds on farm. All birds examined had evidence of mul-tiple granulomatous lesions in the lungs and air sacs that weregrossly consistent with granulomatous aspergillosis nodules.

Moderate amounts of Aspergillus species were isolated onculture of lung tissue from six birds examined at this visit.

Histological examination of various tissues collected from thebirds examined on day 10 are shown in table 1.

Table 1 Histological examination of various tissues collected fromthe birds examined on day 10

Tissue Histological findings

Liver Mild congestion with a diffuse foamy vacuolation of hepatocytecytoplasm (consistent with either fat or glycogen deposition).

Spleen A few granulocytes were present in subcapsular regions andoccasional foci within the parenchyma.

Lung 1 An airway contains ciliated epithelium and there is hypertrophy ofbronchiolar-associated lymphoid tissue focally with occasionalgranulocytes present and one multinucleate cell in one atrium in anadjacent parabronchus. There are occasional small foci oflymphocytes within parenchyma.

Lung 2 Several granulomas are present within the lung parenchymaconsisting of necrotic centres and degenerate inflammatory cellswith some surrounding multinucleate cells and a degree ofmononuclear cell infiltration. Possible cross sections of hyphal formsare seen in some. There was an adjacent granulomatousairsacculitis with areas of necrotic cellularity, degenerategranulocytes and multinucleate cells with the suspicion of hyphalforms. Intervening connective tissue contained macrophages,granulocytes and early fibroblasts. A second section showed a moreseverely affected piece of lung with several granulomas surroundedby fibrosis and loss of lung parenchyma.

Lungtissues

There was evidence of a chronic multifocal granulomatouspneumonia in multiple lungs examined. The Periodic acid–Schiff-stained sections undertaken from lung tissue showedbranching septate fungal hyphae associated with the granulomasand the lesions in the lung were consistent with a mycoticpneumonia and the branching septate nature of the fungal hyphaeis consistent with aspergillosis.

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A straw sample collected from house 3 was analysed to assessmicrobial growth using standard microbiological techniques.The sample was collected from the centre of a partially usedbale within the shed. The sample had a profuse growth of totalbacteria (>2000 colony-forming units (cfu)/g) and Enterococcus(2100–20,000 cfu/g), with moderate growths of coliforms (210–2000 cfu/g) and yeasts and moulds (210–2000 cfu/g). Some ofthe fungal colonies were identified grossly as Aspergillus species.While there are no set values for bacterial and fungal contamin-ation of straw bedding, bedding for brooding poultry stockshould be less than 20 cfu/g for enterobacteria and Aspergillusspp.

DIFFERENTIAL DIAGNOSISDifferential diagnoses considered on the initial examination andvisit were:

▸ Carbon monoxide poisoning▸ Acute bacterial septicaemia▸ Mycotoxicosis

TREATMENTNo specific treatment is licensed or available for treatment ofacute respiratory aspergillosis in poultry. The birds werere-bedded with better quality straw to separate them as much aspossible from the contaminated bedding. Unfortunately it wasnot possible to move them to different accommodation, so theywere completely removed from the contaminated bedding.Supportive therapy of multivitamins was also administered.

OUTCOME AND FOLLOW-UPThe final cumulative mortality in house 2 was 60 per cent whenthe ducks were processed at 45 days of age. The cumulativemortality in shed 3 was 52 per cent when the ducks were pro-cessed at 52 days of age. Processing rejects in both batches ofbirds were less than 1.5 per cent, which is within budget levelsfor the company.

DISCUSSIONThe final diagnosis was made on the clinical and gross post-mortem findings on day 10, with the support of histology andmicrobiology (Chute and Richard 1997, McMullin 2004).

Following the rapid, obvious response in the birds withincreased ventilation at the time of the initial site visit, in con-junction with the reddening/hyperaemia of the lungs, carbonmonoxide toxicity was suspected as contributing to the mortal-ity (Hoerr 1997, Jordan and others 2001). However, the broo-ders were subsequently checked by a qualified gas engineer andappeared to be in good working order and carbon monoxidelevels were undetectable in the houses. In addition, the fact thatby day 9 posthatch both houses were encountering high mortal-ity made carbon monoxide poisoning due to poorly functioningbrooders less likely.

Although the hyperaemia of the lungs was noted at the timeof the initial postmortem examination, there were no other

gross pathological lesions to suspect aspergillosis. Acute pul-monary aspergillosis usually presents with multiple granuloma-tous lesions in the parenchyma of the lungs (Hubben 1958,Arne and others 2011). These ducklings must have beenexposed to such high numbers of aspergillosis spores that anacute inflammatory reaction ensued prior to the development ofgranulomatous lesions. Gliotoxins have been identified inturkeys infected with Aspergillus spp. and are considered to beinvolved in the pathogenesis of Aspergillus infections in poultry(Richard and DeBey 1995). The authors were not able tomeasure the gliotoxin levels in these birds. Microbiology on theinitial postmortem submission and also those submitted to theAHVLA laboratory did not include specific cultures for fungiand moulds. In future we would advise that fungal cultures areincluded in acute mortality cases of ducklings.

The most likely source of the Aspergillus spp. was the strawbedding; high fungal counts were identified on culture. Weatherconditions for the previous harvest were wet, and any fungalcontamination of straw bales would have been exacerbated bystorage of the bales within the brooding environment. Theoptimum temperature for Aspergillus fumigatus replication is40°C (Hayden and Maude 2007); increased fungal replicationwill occur when temperatures rise above 23°C. Egg contamin-ation was eliminated as the source because previous and subse-quent placement of ducklings from the same parent source wasnot affected.

Initial differential diagnosis included mycotoxicosis, hence itwas advised to re-bed with fresh straw and to change the feed.Although moniliformin (Fusarium moniliformin) mycotoxin wasconsidered (Leeson and others 1995), its presence was nottested for in straw or feed due to the cost and the time takenfor analysis.

Competing interests None.

Patient consent Obtained.

Provenance and peer review Not commissioned; externally peer reviewed

REFERENCESARNE P., THIERRY S., WANG D., DEVILLE M., LE LOC’H G., FEMENIA F., NIEGUITSILA A.,HUANG W., CHERMETTE R., GUILLOT J. (2011) Aspergillus fumigatus in Poultry.International Journal of Microbiology 2011, 1–14. article id 746356 14 pages

CHUTE H. L., RICHARD J. L. (1997) Fungal Infections. Diseases of Poultry. 9th edn. IowaState Univeristy Press. 351–360

HAYDEN N. J., MAUDE R. B. (2007) The effect of heat on the growth and recovery ofAspergillus spp. from the mycoflora of onion seeds. Plant Pathology 43, 627–630

HOERR F. J. (1997). Diseases of Poultry. 10th edn. Iowa State University Press. 951–1005HUBBEN K. (1958) Aspergillus Menigo-Encephalitis in turkeys and ducks. Avian Diseases2, 110–116

JORDAN F., PATTISON M., ALEXANDER D., FARAGHER T. (2001) Poultry Diseases.5th edn. W.B.Saunders. 513–514

LEESON S., DIAZ G., SUMMERS J. D. (1995) Poultry Metabolic Disorders and Mycotoxins.Nottingham University Press. 310–332

MCMULLIN P. F. (2004) A Pocket Guide to Poultry Health and Disease. 1st edn.5m Enterprises. 75–76

RICHARD J. L., DEBEY M. C. (1995) Production of gliotoxin during the pathogenic statein turkey poults by Aspergillus fumigatus Fresenius. Mycopathologia 129, 111–115

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ducklingsAcute respiratory aspergillosis in commercial

Daniel Parker and Andrew Walker

doi: 10.1136/vetreccr-2013-0000242014 2: Vet Rec Case Rep 

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