Outbreak of infectious laryngotracheitis in large multi-age egg layer chicken flocks in Minas Gerais, Brazil

Abstract

A recent (November 2010) outbreak of infectious laryngotracheitis (ILT) in a multi-age laying hen facility in Minas Gerais state, Brazil, is described. Previous ILT outbreak in laying hens was only notified in São Paulo state, Brazil, in 2002. In the outbreak described here, the affected population was approximately eight million hens, with flock sizes ranging from 100,000 to 2,900,000 chickens. The average mortality ranged from 1 to 6%, and morbidity was around 90% (most of the twenty seven farms of the area were positive for ILT virus). Three multi-age laying farms from one company were selected for this report. Clinical signs included prostration, dyspnea, conjunctivitis, occasional swelling of the paranasal sinuses and bloody mucous nasal discharge. Severely affected chickens presented with dyspnea, gasping and became cyanotic before death. At necropsy, these chickens had fibrinous exudate blocking the larynx and the lumen of cranial part of the trachea. In addition, conjunctivitis with intense hyperemia, edema and sinuses with caseous exudate were present. On histopathology, there were marked necrosis and desquamation of respiratory ephitelium and conjunctiva with numerous syncytial cells formation and fibrinous exudate. Moderate to marked non suppurative (especially lymphocytes and plasma cells) infiltration in the lamina propria also was observed. Sixteen out of 20 examined chickens, eosinophilic intranuclear inclusion bodies were observed in the syncytial cells. The DNA extracted from larynx and trachea produced positive PCR results for ILT virus (ILTV) DNA using formalin-fixed, paraffin embedded (FFPE) samples. Amplicons from a small region of ICP4 gene were submitted to sequencing and showed 100% identity with ILTV EU104910.1 (USA strain), 99% with ILTV JN596963.1 (Australian strain) and 91% with ILTV JN580316.1 (Gallid herpesvirus 1 CEO vaccine strain) and JN580315.1 (Gallid herpesvirus 1 TCO vaccine strain).

Enfeksiyöz Laringotraheitis İle Doğal Enfekte Yumurta Tavuklarında Solunum Kanalı Lezyonları Üzerine İmmunohistokimyasal Çalışmalar

“…In seven cases, both bloody-mucopurulent and diphtheroid exudate were noted. In particular, the exudate accumulation in the tracheal lumen was similar to the findings reported by researchers [14,17,21,26] . In infraorbital sinus, mucous exudate was detected in 16 cases.…”

“…Polymerase chain reaction analysis of the ICP4 gene was performed using the primers ICP4-1F (5'-CCT TGG TTC GGG AT¬G AAA CC-3') and ICP4-1R (5'-TTC ATT ACC TCC AGC GGT TCC-3') described by Preis et al [14] . These primers showed a single amplicon, the size of which was 237 bp.…”

“…Although findings were observed in all (100%) cases in histopathology, ILT specific inclusion bodies were detected in 30 (50%) cases in the larynx and trachea. Preis et al [14] found inclusion bodies in the trachea (70%), larynx (50%), and lung (10%). This suggests that reduces the reliability of the histopathological diagnosis.…”

Pathological, immunohistochemical, and molecular findings in commercial laying hens and in backyard chickens naturally infected with the infectious laryngotracheitis virus

“…The etiologic agent can be identified by viral isolation, direct immunofluorescence, DNA hybridization, and Polymerase Chain Reaction (PCR) (Guy & Garcia, 2008). The GaVH-1 was detected in Brazil by Hipólito et al (1974), Beltrão et al (2004), Chacón et al (2007), and recently by Preis et al (2013) in multi-age egg laying chickens in a high poultry density farm. The aim of this study was to describe lesions and virus distribution in different tissues of chickens naturally infected with GaHV-1 using IHC and PCR.…”

Epidemiology of Avian Infectious Laryngotracheitis with Special Focus to South America: an update

“…In the state of Minas Gerais, there was an outbreak in the 2010 in multi-age laying hen farms (Preis et al, 2013), caused by a low-virulence field strain. The Brazilian authorities authorized the use of only vectored vaccines in this region for the prevention of new cases (Couto et al, 2014).…”