Schistosomiasis treatment improves CD4 count, viral load in HIV-positives

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Treatment of the parasitic infection schistosomiasis (also known as bilharzia) results in a stabilisation in HIV viral load and an improvement in CD4 cell count in HIV-positive people, Danish and Zimbabwean researchers report in the December 1st edition of the Journal of Infectious Diseases.

Schistosomiasis is a widespread parasitic infection in southern Africa. It is a debilitating parasitic disease caused by five different kinds of flatworm or blood fluke (helminth). 500 to 600 million people are at risk worldwide, in 74 countries, of whom 20 million are severely ill, another 120 million have some symptoms and another 60 million or more are infected. Its economic impact is second only to malaria, in reducing productivity at work and in limiting children’s ability to learn.

It is common in large parts of Africa with two main kinds – S. mansoni (whose eggs are shed into faeces) and S. haematobium (whose eggs are shed into urine). Eggs pass into water where they rest on water plants, until eaten by snails where they grow into larvae that are then shed into fresh water. These larvae then pass into the bodies of people who enter the water.

Glossary

disease progression

The worsening of a disease.

drug interaction

A risky combination of drugs, when drug A interferes with the functioning of drug B. Blood levels of the drug may be lowered or raised, potentially interfering with effectiveness or making side-effects worse. Also known as a drug-drug interaction.

p-value

The result of a statistical test which tells us whether the results of a study are likely to be due to chance and would not be confirmed if the study was repeated. All p-values are between 0 and 1; the most reliable studies have p-values very close to 0. A p-value of 0.001 means that there is a 1 in 1000 probability that the results are due to chance and do not reflect a real difference. A p-value of 0.05 means there is a 1 in 20 probability that the results are due to chance. When a p-value is 0.05 or below, the result is considered to be ‘statistically significant’. Confidence intervals give similar information to p-values but are easier to interpret. 

log

Short for logarithm, a scale of measurement often used when describing viral load. A one log change is a ten-fold change, such as from 100 to 10. A two-log change is a one hundred-fold change, such as from 1,000 to 10.

malaria

A serious disease caused by a parasite that commonly infects a certain type of mosquito which feeds on humans. People who get malaria are typically very sick with high fevers, shaking chills, and flu-like illness. 

The schistosomiasis and HIV cohort was established in Zimbabwe to look at the interaction between schistosomiasis and HIV, following the observation that generalised immune activation caused by schistosomiasis might increase the rate of HIV disease progression.

As part of the cohort’s research a randomised study was carried out to test the effects of schistosomiasis treatment in HIV-positive people. The study randomised 287 people with and without HIV infection who were infected with schistosomiasis to receive immediate treatment with praziquantel or treatment deferred for three months.

Two hundred and twenty-eight participants were available for follow-up, of whom 130 were HIV-positive. Comparison between HIV-positive participants who received immediate treatment and those who received deferred treatment showed a difference of –0.21 log10 copies/ml after three months, favouring the immediate treatment group (p=0.03). In the deferred treatment group viral load continued to rise whilst it stabilised in the immediate treatment group.

CD4 counts rose in all patients who received treatment irrespective of HIV status, suggesting that schistosomiasis is a widespread cause of immune suppression in Africa, and further highlighting the need for cohort studies in sub-Saharan Africa outside South Africa that can quantify the relationship between viral load, CD4 count and disease progression, in order to determine whether there are regional differences in the predictive value of internationally recognised thresholds such as a CD4 cell count of 200 cells/mm3.

Using data from a European cohort, the authors estimate that a decrease in viral load of –0.21 log10 copies/ml would be associated with a reduction in mortality of between 1.9 and 7-fold. However they caution that the 95% confidence interval for the viral load change was between –0.39 log and 0.02log10 copies/ml, and that another study has shown any suppressive effect of schistosomiasis treatment on HIV viral load disappearing after six months. They conclude that while their study supports the view that schistosomiasis increases HIV viral load, further operational research is needed to determine whether schistosomiasis interventions should be incorporated into the current initiatives for providing antiretroviral treatment in areas where both infections are endemic.

References

Kellestrup P et al. Schistosomiasis and HIV-1 infection in rural Zimbabwe: effect of treatment of schistosomiasis on CD4 cell count and plasma HIV-1 RNA load. J Infect Dis 192 (online edition), 2005.