Inclusion Body Rhinitis

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Also Known As: IBR — Cytomegalic Inclusion Disease

Caused By: Porcine Cytomegalovirus — Suid Herpesvirus 2 — SHV-2 — Inclusion Body Rhinitis Virus — Pig Cytomegalovirus — IBRV — PCMV

Introduction

Cytomegalovirus infection histology - note basophilic nuclear inclusion bodies and peri-nuclear halo. Wikimedia Commons

Porcine Cytomegalovirus is a herpesvirus causing Inclusion Body Rhinitis in pigs.

PCMV may pose a risk to humans through transplanted organs and this is currently being researched. It is not currently considered a zoonosis due to its host range being highly restricted to only the pig.

Epidemiology

Global. No country has established freedom from or eradication of disease. Prevalence of infected herds and infected pigs within a herd is very high albeit with a low incidence of clinical disease.

PCMV can cross the placenta facilitating vertical transmission. Horizontal transmission between infected pigs is also important.

Signalment

Clinical signs are largely restricted to piglets under 3 weeks of age. They can be infected in utero or as neonates.

Clinical Signs

Respiratory signs:
Rhinitis is most common, causing snuffling, sneezing, coughing, production of purulent/catarrhal discharge, increased lacrimation, conjunctivitis, ocular discharge, epistaxis, dyspnoea.
Pneumonia may occur.

Anorexia, anaemia, lethargy, pyrexia and sudden death may all be noted.

Reproductive failure caused by PCMV is characterised by abortion, mummified piglets and birth of stillborn, weak or stunted pigs. Ulcers and erosions may form on the external genitalia. Sows may develop agalactia.

Gastrointestinal and neurological signs can also develop.

In common with all herpesviruses, PCMV can become latent and recrudesce with stress.

Diagnosis

Diagnosis is often based by the observation of mummified or weak litters along with signs of rhinitis and respiratory disease on a unit.

Black discolouration around the eyes due to conjunctival exudate is also suggestive.

Antigen can be detected serologically by fluorescent antibody test (FAT).

Antibody can be detected by Indirect Fluorescent Antibody Test (IFAT) and ELISA.

PCR tests for PCMV have now also been developed and are very sensitive.

On post-mortem, petechiation of the heart, kidneys, intestine, lungs, lymph nodes and meninges is seen in neonatal and foetal pigs. Pulmonary congestion is marked and the bronchial and mediastinal lymph nodes are dramatically enlarged. Ventral aspects of lung lobes are often discoloured purple. The nasal mucosa is congested with a mucoid exudate.

Histologically, large basophilic intranuclear inclusion bodies are present in the mucosal epithelial cells of the turbinates, salivary glands and kidney tissues.

Electron microscopy can also be used for the same purpose.

Smears from the nasal mucosa of pigs at slaughter can also be used to identify inclusion bodies.

Treatment

Natural outbreaks often resolve without intervention.

Control

No vaccine has been developed for PCMV.

Reducing stress especially when new stock is introduced and minimising the mixing of litters may reduce severity and frequency.

No national control schemes are in place.

Inclusion Body Rhinitis Learning Resources
Flashcards Test your knowledge using flashcard type questions	Porcine Cytomegalovirus Flashcards

References

This article was originally sourced from The Animal Health & Production Compendium (AHPC) published online by CABI during the OVAL Project. The datasheet was accessed on 16 June 2011.