Tuberculosis (TB) kills two million people and infects nine million every year, and those numbers are rising, especially in southern Africa, which has the highest rates of HIV. TB-HIV co-infection is already a major problem and it is only getting worse, in part because of a lack of effective diagnostic tools and treatments. Dr. Peter Saranchuk was the medical coordinator at MSF’s HIV/AIDS project in Lesotho. Here, he explains the reasons behind the dangerous relationship between TB and HIV.
Why are so many people affected by HIV also affected by TB?
HIV slowly makes a person’s immune system weak over time, so they suffer from more infections, and these infections get more and more serious as time goes on. If a person is exposed to someone with TB in their household, everyone in that household is exposed. Normally, TB stays dormant inside the body, but if that person gets sick, and their immune system gets weak, then the TB germ starts to grow and cause active disease.
So if it’s TB of the lungs (pulmonary TB), they start to cough, sweat at night, have a high temperature, lose their appetite, and lose weight, and this person with active TB slowly gets sick over time.
Does TB take a different course throughout the bodies of people infected with HIV than the bodies of healthy individuals?
Yes. And the reason is that the immune system is weaker and the body produces less sputum. When an HIV-positive person coughs, they only cough up a few TB germs in their sputum, and since people are tested for TB through sputum samples it’s very difficult to diagnose TB in an HIV-positive person.
So, when this person coughs, they provide a sputum sample to the lab; it gets processed in the lab; the lab tech looks under a microscope at the slide; and, even though the person has TB, they’re not coughing up enough TB germs for it to be detected under a microscope. That’s what we call “smear-negative” TB, and the vast majority of people with pulmonary TB are smear-negative, so the traditional test for TB using the microscope really doesn’t help us much these days.
That also means it’s very difficult to diagnose people with TB, and more importantly, the diagnosis is delayed, so they end up getting sicker and sicker and the TB symptoms get worse and worse, and often they have to get admitted to hospital in order to get the TB diagnosed.
There are other ways to diagnose the TB—by chest x-ray sometimes we can tell. We can also send the sputum sample for TB culture, where we try to grow the TB germ in the lab, but that takes many weeks, and once again, the diagnosis is delayed.
The second major type of TB that often HIV-positive people get is called extra-pulmonary TB—that’s TB causing disease outside of the lungs. So, TB, it’s quite incredible—it can affect almost any part of the body. People can get TB meningitis—that’s TB of the fluid around the brain and the spinal cord. People can get abdominal TB—inside the abdominal cavity. People can get disseminated TB—involving pretty much all of the body. There is TB of the joints. Women can get TB of the breast. I’ve seen people with TB of the thyroid gland . . . pretty much any part of the body; it’s quite incredible.
And in terms of treating TB when someone has HIV, are there implications in terms of the drugs for both diseases interacting? If you find out first that the person has TB or if you find out at the same time that they have TB and HIV, how do you proceed then?
TB treatment in itself is quite complicated. We have to use at least four TB drugs initially. Sometimes they have side effects, so we have to watch for side effects in a person taking TB drugs.
If that person is HIV positive, usually their CD4 count, or their immune system, is quite weak, so that person also needs treatment against HIV. That means another set of drugs called antiretrovirals (ARVs), of which a person needs to take at least three.
Now they’re taking four TB medications and if their immune system is quite weak we start them on an additional three ARVs. There are possible interactions between these drugs, so we have to watch them closely and clinically check on them quite regularly. And we have to do lab tests, as well, to check the liver function, for example, to make sure that neither the TB drugs nor the ARVs are causing a problem. But that’s not easy for someone living in a remote mountain setting, as many people do in Lesotho.
How do we get a person to have the monitoring lab tests? Well, what we’ve done in our setting is have the person come to the clinic, their blood is taken at the clinic, and we arrange for a regular specimen collection and transport to the lab. A few days later, the specimen vehicle comes back to the clinic with the lab results. It saves the patient a lot. And this is one of the objectives of our program—to have decentralized care—so that care comes to the patients as opposed to all the patients coming to the hospital.