Third Eyelid Syndrome

Other names: Diarrhoea and Third Eyelid Syndrome; Torovirus Infection.

Contents

 Introduction

 Symptoms

 Causative Agent

 Treatment

 References

Introduction

The diarrhoea and third eyelid syndrome has long been recognised in cats, but until recently, nothing was know about the cause. When my cat, Oscar, was diagnosed with this condition, I searched the Internet for information, but unfortunately found nothing about the disease. What I have gleaned from posters to rec.pets.cats.health+behav, books and research papers I have condensed into this page. Enjoy!

Back to top

Symptoms

The symptoms of this disease are generally mild. Owners often panic that their cats are suffering from feline influenza,but this is not the case - it's more like a head cold than 'flu.

Protruding nicitating membranes (haws, third eyelids). These usually only protrude part of the way across the eyes, rather than covering the eyeball completely.  The eyes may seem watery, perhaps with a little clear discharge (like tears).

Diarrhoea. This is not always obvious in a cat unless they always use a litter box (i.e. never go outside unaccompanied), they have faecal soiling of the fur around their back ends or they have an accident in the house. It may persist for days, weeks or months, but the cat seems otherwise bright.

Sneezing. This is not a universal symptom, and often manifests as single, rather than repeated, sneezes.

Other general signs. These include vomiting, drowsiness, slight fever, irritability, anorexia (loss of appetitie) and generally seeming "off-colour".

Back to top

Causative Agent

The cause of this condition is a virus. The Torovirus is a member of the same family of viruses as the Coronaviruses. A Coronavirus is the cause of Feline Infectious Peritonitis (FIP), but the Torovirus is much milder. The condition is usually mild and self limiting.

The virus has the following structure;

 

The Torovirus is a class IV virus, a member of the Coronaviridae. It has a single stranded positive sense RNA genome, 27 to 30 kbp in length. The protein spikes that surround the envelope are club shaped and give the virus its name as it looks like a crown. It replicates in the cytoplasm of the cell, rather than the nucleus. It has an irregular and sometimes biconcave shape (middle diagram). When looked at under the electron microscope it appears as in the right diagram. It is 130 nm in diameter.

If you wish to see the rather technical relication cycle of the virus, click here.

Toroviruses cause diseases in man and many animals, including cows and cats. It is disputed whether the diarrhoea in the feline infection is caused by secondary bacterial infection or the virus. My personal suspicion is that it is caused by the virus, simply because Toroviruses cause gastrointestinal symptoms in other animals.

As with any viral illness, there is a possibility of secondary bacterial infection - this may manifest itself as rhinitis, conjunctivitis, pneumonia or gastroenteritis most commonly, although as the cat will be run down, any infection is more likely to develop.

Back to top

Treatment

Treatment of torovirus infection is generally supportive - that is, keeping the cat comfortable by providing plenty of fresh water to drink (prevent dehydration from the diarrhoea and fever), a bland diet (eg: chicken or white fish, rice, or a prescription diet) to rest the gut following a 24 hour fast if diarrhoea is severe and wiping any discharge from the eyes. Some vets will prescribe antibiotics to prevent or treat a secondary bacterial infection. If diarrhoea is persistant, then corticosteroid rablets may be used to dampen down the gut inflammation.

However, like the common cold in their owners, torovirus infection is usually mild and self limiting, lasting 5 to 10 days.

Back to top

References

A new family of vertebrate viruses: Toroviridae.
Horzinek MC, Flewett TH, Saif LJ, Spaan WJ, Weiss M, Woode GN
Intervirology 1987 27:1 17-24

Toroviridae: a proposed new family of enveloped RNA viruses.
Horzinek MC, Weiss M, Ederveen J
Ciba Found Symp 1987 128: 162-74

A new group of gastrointestinal viruses ("Toroviridae")
Weiss M
Schweiz Arch Tierheilkd 1987 Mar 129:3 139-56

The proposed family Toroviridae: agents of enteric infections. Brief review.
Weiss M, Horzinek MC
Arch Virol 1987 92:1-2 1-15

A clinical and microbiological study of cats with protruding nictitating membranes and diarrhoea: isolation of a novel virus.
Muir P, Harbour DA, Gruffydd-Jones TJ, Howard PE, Hopper CD, Gruffydd-Jones EA, Broadhead HM, Clarke CM, Jones ME
Vet Rec 1990 Sep 29 127:13 324-30

The Newsgroup message discussion beginning 14/12/98

Back to top

Last Revised: 3 February, 1999

Email Andy with any further information about this condition.