Cytomegalovirus

Summary

• Cytomegalovirus (CMV) is a common virus that affects almost all adults.
• CMV usually lives harmlessly in the body, but when the immune system is compromised, the virus is activated and can cause infections.
• CMV can attack a number of different organs of the body, including the eye, the oesophagus and the colon.
• In the eye, CMV infects the retina and can cause blindness.
• A biopsy is often necessary to diagnose CMV.
• Drugs used to treat CMV infection include ganciclovir, foscarnet and cidofovir.

Definition

Cytomegalovirus (CMV) is a member of the herpes virus family, and almost all adults are silently infected with it. CMV is found in various body fluids including saliva, blood, urine, semen, vaginal secretions and breast milk. The virus is most commonly transmitted through sexual or close personal contact, while it can also be spread through breastfeeding and blood transfusions.

In a healthy person who is infected with CMV, the immune system prevents the virus from replicating and causing disease. Although never completely eradicated from the body, the virus lies dormant. It is only when the immune system is severely weakened that CMV results in significant disease.

How does cytomegalovirus affect people with HIV/Aids?

A large proportion of people with HIV infection have also been infected with CMV. It is usually in the very late stages of Aids, when the CD4 cell count falls below 100, that CMV is reactivated and can attack a number of organs.

Symptoms

• Cytomegalovirus retinitis: The eye is vulnerable to CMV – specifically the retina, the layer of special light-detecting cells at the back of the eye. Cytomegalovirus retinitis causes failing vision in one or both eyes. If untreated it will eventually cause blindness. The condition is painless.
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• Cytomegalovirus oesophagitis: CMV can attack the oesophagus (the passage between the mouth and the stomach), causing pain in the mid-chest area when food is swallowed.
• Cytomegalovirus colitis: Cytomegalovirus colitis affects the colon, frequently causing diarrhoea, abdominal discomfort, fever and decreased appetite.

Many of the symptoms of CMV are similar to those of other diseases and conditions, which is why a correct diagnosis may initially be difficult. When a person is first infected with CMV they may suffer from a sore throat, swollen glands, tiredness and fever, all of which may be confused with symptoms of other illnesses.

People with CMV may show signs of jaundice, where the skin and eyes appear yellow. Less frequently, CMV can affect the nervous system (neuropathy), causing numbness, pain, or a tingling sensation in the limbs. CMV can also affect the lungs, resulting in pneumonia.

Diagnosis

CMV retinitis can be diagnosed by examination of the retina using a hand-held opthalmoscope. The doctor will see tell-tale haemorrhages (bleeding) and exudates (fluffy spots) on the retina.

In order to diagnose CMV in other organs, it is necessary to perform a biopsy (take a tissue sample). While a simple blood test may show the presence of CMV, it is not evidence enough to conclude that there is active disease. The sample of tissue that is removed is sent to the laboratory where it is studied under a microscope for signs of active CMV disease.

Treatment

There are currently three drugs available for treating CMV infections.

• Ganciclovir can be given intravenously or orally, but in the case of retinitis it is best given as a slow-release implant placed directly in the eye under local anaesthetic. Treatment for CMV retinitis must usually be life-long or the disease will relapse.
• Foscarnet can be used to treat retinitis and other CMV infections, but is only available as an intravenous preparation.
• When ganciclovir and foscarnet are given intravenously, the drug is infused through a small tube (catheter) that goes directly into the chest or arm. Both of these drugs must be infused on a daily basis and the procedure can take up to two hours. The catheter remains in place and must be kept covered, clean and dry to prevent infection.
• Cidofovir can also be used to treat retinitis and other CMV infections, and is also given intravenously. Cidofovir is administered less frequently, but does have more serious side-effects.

There is no cure for CMV disease, but the drugs can alleviate symptoms and stop further injury to the affected parts of the body. However, these drugs have several side effects.

Side-effects of anti-CMV drugs

• Ganciclovir use can result in a low white cell count (neutropenia). This condition is usually without symptoms, but can cause problems when ganciclovir is taken in combination with certain antiretrovirals that also cause a low white cell count. Other side- effects may include nausea, vomiting, diarrhoea, fever, rash, anaemia and abnormal liver function. Complications when placing the retinal implant can result in inflammation of the inside of the eye or retinal detachment.
• Foscarnet can cause metabolic disturbances, skin ulcers, and kidney damage.
• Cidofovir can cause severe kidney damage.

Prevention

The only way to prevent CMV-related illnesses is to keep as healthy as possible. Ensuring that you get the best care for your HIV infection and taking your antiretroviral medication consistently will help prevent a drop in your CD4 cell count and keep CMV infection at bay.

Reviewed by Dr Eftyhia Vardas, University of the Witwatersrand