Encephalomyelitis in 11- and 14-week-old, Brown Layer Chickens - Vaccine-induced?

Fourteen live and eight dead, 11-week-old, and 14 live, 14-week-old, brown layer pullets, from two companies were received at the California Animal Health & Food Safety Laboratory System, Turlock-Branch for laboratory examination with a clinical history of neurological signs, unevenness in size, lethargy, and moderate increase in mortality, reported C. Gabriel Sentíes–Cué University of California, Davis.

The flocks had been vaccinated for avian encephalomyelitis and fowl pox with a live attenuated vaccine in the wing web at nine weeks of age.

At necropsy, the birds were moderately emaciated, crops were empty and gizzards contained mostly litter. The histopathological examination revealed lymphocytic perivascular infiltration and neuronal central chromatolysis in the cerebrum and spinal cord, as well as gliosis in the cerebellar molecular layer.

Avian encephalomyelitis virus was detected by RT-PCR on brain homogenate. Other avian viral infections capable of causing encephalitis, including paramyxoviruses, avian influenza, west Nile, eastern equine encephalitis and western equine encephalitis were ruled out by virus isolation and molecular methodology attempts.

Post-vaccinal Reovirus Hepatitis in Breeder Chicks

Martine Boulianne of the University of Montreal reported an investigation into increased mortality 48 hours post-delivery in a broiler breeder flock.

At necropsy, chicks presented severe subcutaneous sero-sanguinolent exudate in the cervical area, marked hemorrhagic pulmonary edema, splenomegaly, enlarged kidneys and hepatomegaly with multi-focal pinpoint necrotic foci. Bacteriological results were inconclusive. At five days of age, the mortality had reached 10 to 37 per cent in the four pens, with many birds being listless and huddling.

Histopathology revealed severe necrotising hepatitis characterised by numerous hyalinised polykaryocytes with pyknotic nuclei. At eight days of age, birds started to develop septicaemic lesions as well as tenosynovitis.

Due to a mistake in administrating the wrong reovirus vaccine at the hatchery, the breeders’ supplier recommended culling of the remaining flock.

High Early Mortality in Breeder Pullets

Early mortality in breeder pullets can be caused by several factors. Bacterial infection, dehydration are probably two of the most common causes of first week mortality. There can be several other causes such as malfunctions in the incubation process, contamination of a vaccine, vaccine given at the wrong time or Aspergillosis.

Kurt N. Dobson of Simmons Foods presented a case report of an incidence that happened where the formaldehyde was sprayed late in the hatching process and caused tracheal burns in the birds with secondary bacterial and fungal infections.

Aspergillosis with High Mortality in a Broiler Breeder Flock

A broiler breeder farm in the southeast region of The United States presented significant high mortality, starting at 26 weeks of age, reported Alexandra M. Mendoza-Reilley of Ceva Animal Health. Females exhibited signs of weeping vent and possible calcium tetany. The first visit was performed when the flock was 29 weeks of age and sequential visits to the farm were followed.

Sampling was conducted for serological analysis, histopathologic observations, and microbiological examination.

Additionally, fungi evaluation of tracheal plugs and litter shavings were performed. The history, diagnosis and recommendations of this field case were presented at the AVMA convention.

Effect of Calcium Toxicity on Broiler Breeder Pullets

Renal disease was identified as the cause of increased mortality after the onset of lay in several flocks of broiler breeders in Southern Georgia, according to Erin Riley of Sanderson Farms Inc.

Consecutive necropsies displayed a significant number of hens with visceral gout and at least one grossly abnormal kidney. Case history, rule-outs, diagnostics and the impact on egg production compared to non-affected flocks were presented.

Hepatic Necrosis as a Cause of Sudden Increased Mortality in Breeder Replacement Turkeys

Several outbreaks of hepatic necrosis caused sudden increase in mortality in 14- to 25 week-old turkey breeder replacement hens, reported H. L. Shivaprasad of the University of California, Davis.

Mortality ranged from 1.0 to 1.5 per cent in a span of five to six days. Clinical signs ranged from mild depression to none. Necropsy revealed enlarged and mottled red or white livers and some with extensive pale areas at the edges. Microscopically, the lesions consisted of acute multifocal (centrolobular) coagulative necrosis of hepatocytes with sinusoidal congestion and mild to severe hyperplasia of bile ducts.

Several feeds analysed for mycotoxins such as aflatoxins and ionophores were negative. Heavy metals, selenium and vitamin E analysis of the livers were unremarkable. No significant aerobic or anaerobic bacteria were isolated from the livers. Virus particles in the range of 25 to 30nm in diameter were identified in the livers of a few birds by electron microscopy.

Outbreak of Chlamydiosis with Unusual Clinical Signs and Pathology

Chlamydiosis is a naturally occurring contagious systemic and zoonotic disease of various species of birds including turkeys caused by Chlamydophila psittaci.

H.L. Shivaprasad of the University of California, Davis described an unusual outbreak of Chlamydiosis confirmed by FA, IHC and PCR occurring in a 13-week-old organically grown flock of turkeys.

The disease was characterised by unilateral or bilateral swelling of nasal glands above the eye. The birds did not exhibit any respiratory signs nor there an increased mortality in the flock.

The dilemma faced by the owner whether to treat or not to treat for chlamydia in an organically grown turkeys and the refusal by the FSIS to process the turkeys were presented.

Also the importance and significance of this unique chlamydia affecting the nasal glands in the context of testing, zoonotic potential and outcome of the disease will be presented.

Diagnostic Differentiation of Trichomonosis and Histomonosis Co-infection in a Turkey

Trichomonosis and histomonosis are protozoal parasitic diseases of birds. Histomonas meleagridis is the causative agent of histomonosis, also referred to as ‘blackhead’, reported Daylene Mills of the California Animal Health and Food Safety Laboratory. Trichomonas gallinae is known to cause avian trichomonosis, and is commonly found in pigeons, wild doves and falcons, but outbreaks have occurred in domestic fowl. Both parasites are flagellates and belong to the group of parabasalids.

This case report involves an adult turkey that was presented with recumbency, dyspnea and lethargy. Diagnosis of histomonosis was made from pathognomonic gross lesions and histopathology. Furthermore, severe lesions in the upper intestinal tract were found.

Therefore, a polyclonal antibody against Trichomonas foetus was utilised for immunohistochemistry to identify trichomonads on oesophagus, crop and caecal microscopic sections. The immunohistochemistry stained the trichomonad organisms in the oesophagus and crop but also revealed a cross-reaction with the histomonads present in the caecum.

Further immunohistochemistry, in-situ hybridisation and polymerase chain reaction were performed specifically to differentiate and localise the protozoa in various organs.

To the authors’ knowledge, trichomonosis and histomonosis co-infection involving the upper and lower intestinal tract of turkeys has not been previously reported.

Resurgence of Histomoniasis in Small Turkey and Game Bird Flocks in Indiana

Recently there has been a spike in Histomonias is in small specialty flocks of heritage turkeys, chukars and pheasants in Indiana, reported Patricia S. Wakenell of Purdue University.

Not all of the cases have involved exposure to chickens or environment where chickens have been raised. In her presentation, she discussed the diagnosis, treatment and/or management of Histomoniasis in small flocks.

September 2013