Last week, I wrote about co-infection of HIV with tuberculosis but today I want to talk about a disease, which we at the Medical Research Foundation and Centre see even more frequently than tuberculosis.

It was extremely rare in adults before the era of AIDS. It is called toxoplasmosis and is caused by infection with a protozoa, a unicellular organism of the animal kingdom, of the genus Toxoplasma (derived from toxo meaning ’poison’ or ’toxin’ + plasma). It all has to do with cats. They are the definitive hosts of the organism.

The cat gets infected by eating contaminated raw meat, wild birds or mice and the toxoplasma organisms undergo sexual reproduction in the intestines of the cat. As a consequence, the cat has millions of oocysts (eggs) in its faeces. Human acquisition of infection occurs via contaminated soil, salads and vegetables or by the ingestion of raw or undercooked meat (beef, lamb or pork) containing tissue cysts, hence the importance of washing fruits and vegetables thoroughly before eating and cooking, especially by patients who are HIV-positive. However, toxoplasma infection only results in an uneventful subclinical and latent illness in immuno-competent normal adults.

The prevalence of latent infections with toxoplasma varies between regions and peoples throughout the world and increases with age, eating habits, hygiene and climate. For example, by the fourth decade of life, 90 per cent of the French population, who are in the habit of eating rare or medium-rare steaks, carry toxoplasma antibodies in their blood as opposed to only 12.5 per cent of the population in Japan where raw fish is more popular than raw meat. So what are the figures for Trinidad & Tobago?

In 1958, a general population research survey of antibodies to toxoplasma found that 54.5 per cent of us are healthy carriers of these antibodies, meaning that we have been exposed to this infection in the past. However, whereas infection with this organism is asymptomatic and clinically unremarkable in immuno-competent individuals, once anyone suffers from an immune deficiency syndrome like AIDS, there is a high risk of reactivation of the latent toxoplasma cysts in the body, especially in the brain, resulting in severe disease and death if left untreated.

Reactivation of infection in people with HIV/AIDS predominantly causes toxoplasma abscesses in the brain but clinical disease outside the brain is extremely rare. These patients frequently present headaches, confusion, fits and strokes. However, unlike the common stroke, which results from high blood pressure and diabetes, stroke in HIV/AIDS patients suffering from toxoplasmosis are eminently treatable if diagnosed early, and after a month or two with appropriate antibacterial drugs most of these patients recover completely. We have seen many such ’miracles’ in our HIV/AIDS patients, who after treatment, literally take up their beds and walk - without the touch of the Master’s hand.

Now, I did say that toxoplasmosis is very rarely seen in the immuno-competent adult patient and that clinical toxoplasmosis in sites other than the brain is also a rarity. Here, however, is the story of a most interesting HIV-negative lady, who presented to the consultant gastroenterologist at the Port of Spain General Hospital complaining of severe upper abdominal pain and weight loss. A CT scan showed a very large pancreas and the report read: ’Probably cancer of the pancreas or pancreatitis.’

However, because of the prolonged duration of her illness and other factors, this diagnosis was in question and a detailed occupational history of the patient then revealed that gardening was her main hobby and that there were dozens of stray cats in the area where she lived, roaming, romping and obviously also excreting in her garden. It was then that the penny dropped. The extremely rare diagnosis of toxoplasmosis of the pancreas was made.

In short, the burden of infection with the toxoplasma organisms to which she was exposed over the years was so high that it overwhelmed her normal immuno-competent defence. It was the first case of toxoplasma infection of the pancreas reported in Trinidad & Tobago. After appropriate treatment with high doses of sulphur tablets, her ’cancer of the pancreas’ disappeared completely.

Now, here’s new news for you. Just as there is a human immunodeficiency virus (HIV), there is also a feline (cat) immunodeficiency virus (FIV), which attacks the immune system of cats. It is caused by the same family of retroviruses that triggers AIDS in humans. It is called ’feline AIDS.’ The virus was first discovered in 1986 from cats that exhibited a syndrome similar to human AIDS, which was discovered in 1984.

It is estimated that between one to 14 per cent of cats are infected with FIV. The disease, however, is transmitted from cat to cat by blood and especially saliva but not by sex (in the garden) and certainly not by sex on a hot tin roof. It is spread primarily through biting and scratching and free-roaming outdoor male cats that fight each other defending territorial turf are at greatest risk and have an infection rate two to three times that of their female counterparts. Interestingly, cats with feline AIDS sometimes also suffer from toxoplasmosis.

Fortunately, transmission among household cats through normal contact is very unlikely nor can the disease be transmitted from cats to humans. That is the good news. The bad news is that the time I have spent synopsising this article for easy reading has exhausted me so much that, if you would excuse me, I will now try to take a little cat nap.