Prevalence and risk factors for blood filariasis among HIV-infected adults in Gabon, Central Africa: a pilot study

BACKGROUND

The level of blood filariasis parasitaemia as well as the frequency of and the relationship between cotrimoxazole prophylaxis (CTX-P), antiretroviral therapy (ART) intake and CD4 cell count among people living with human immunodeficiency virus (PLHIV) in rural areas of Gabon were being studied.

METHODS

Sociodemographic data and recent biological tests of PLHIV and HIV-negative participants were collected. Loa loa and Mansonella perstans microfilaria were detected by direct microscopy examination and leucoconcentration.

RESULTS

Overall, 209 HIV-positive and 148 HIV-negative subjects were enrolled. The overall prevalence of microfilaria was comparable between PLHIV (19.9% [n=41/206]) and HIV-negative participants (14.8% [n=22/148]) (p=0.2). The L. loa infection rate was comparable between HIV-positive (9.2%) and HIV-negative participants (6.8%) (p=0.2), while the M. perstans infection rate was 14-fold higher among PLHIV (p<0.01). L. loa parasitaemia was 6-fold lower in PLHIV receiving CTX-P (median 150 mf/mL [interquartile range {IQR} 125-350]) than in patients without (900 [550-2225]) (p<0.01). Among subjects with a CD4 cell count <200 cells/μL, the prevalence of M. perstans was 7-fold higher than that of L. loa (20.6% vs 2.9%).

CONCLUSIONS

This study suggests a similar exposure to L. loa infection of PLHIV and HIV-negative patients while M. perstans is more frequently found in HIV-positive individuals, notably those with a CD4 count <200 cells/μL.

Anaemia in asymptomatic parasite carriers living in urban, rural and peri-urban settings of Gabon

Background

This cross-sectional study was carried out in different settlements of Gabon to determine the influence of single or multiple parasite carriage on haemoglobin (Hb) levels.

Methods

Between April 2015 and June 2016, healthy volunteers from urban, peri-urban and rural areas were screened for malaria, blood filariasis and intestinal parasitic infections using microscopic methods. Hb concentration was measured with a Hemocue analyser. The association between parasite carriage and anaemia was assessed.

Results

Among the 775 volunteers examined, 319 (41.2%) were from rural villages and 76.0% were adults. Filariasis, intestinal parasitic infections, Plasmodium falciparum and polyparasitism were detected in 15.6, 14.6, 9.5 and 6.8% of participants, respectively. Anaemia prevalence was 72.6%, with rates of mild, moderate and severe anaemia being 30.9, 61.1 and 8.0%, respectively. The median Hb level was lowest in the presence of hookworms (7.1 g/dl [interquartile range {IQR} 6.8–7.5]), Schistosoma intercalatum (6.9 g/dl), Trichuris trichiura (10.1 g/dl [IQR 8.9–11.5]) and Plasmodium falciparum (10.0 g/dl [IQR 9.1–11.2]) compared with filariaemia (12.1 g/dl [IQR 10.5–13.2]) (p=0.03). Moderate to severe anaemia predominated among those single-infected with P. falciparum (69.5%) or co-infected with intestinal parasitic infections and P. falciparum (76.2%), while it was found in only 23.2% of individuals with filariasis. All participants with soil-transmitted helminths and more than half with a Blastocystis sp. (68.8%) infection had moderate anaemia.

Conclusions

The prevalence of anaemia is high. Asymptomatic parasite carriage is associated with anaemia in this surveyed population in Gabon.

High Frequency of Pfcrt-76T Allele in Plasmodium falciparum Isolates From Gabon and Ivory Coast After the Withdrawal of Chloroquine

The aim of this study was to assess the proportion of Pfcrt-76T mutant allele four years after the adoption of new malaria control guidelines in Gabon and Ivory Coast. Frequency of K76T mutation of Pfcrt gene was compared between Plasmodium falciparum isolates from Gabon and Ivory Coast. Samples were collected in 2008 in Gabon and in 2009 in Ivory Coast. In total, 151 isolates were selected and analysed by nested-PCR-RFLP for Pfcrt-76 allele identification: 63 in Abobo (Ivory Coast) and 78 in Oyem (Gabon). The proportion of Pfcrt-76T mutant allele was higher in Oyem (70%) compared to Abobo (46%) (p=0.005). This allele was more frequently detected in patients less than 5 years old in Oyem (75 %) compared to Abobo (52%) (p<0.01). The present work showed different prevalence of Pfcrt-76T allele between both sites probably due to a different drug pressure on P. falciparum strains circulating in these areas. Moreover, a decrease of the mutation frequency is observed compared to data obtained in 2005. Therefore, a continuous monitoring of this allele and other drug resistance molecular markers is required in these countries.

Decrease of microscopic Plasmodium falciparum infection prevalence during pregnancy following IPTp-SP implementation in urban cities of Gabon

BACKGROUND

Six years after the implementation of intermittent preventive treatment in pregnancy (IPTp) with sulfadoxine-pyrimethamine (SP) in Gabon, its impact on placental malaria and pregnancy outcomes remains unknown.

METHODS

Age, gestational data, use of IPTp-SP and birth weight were recorded during a hospital-based cross-sectional survey performed in 2011 in 387 women at the end of pregnancy.

RESULTS

Malaria prevalence was 6.7 and 5.3% in peripheral and placental blood respectively. Overall, 59.0% women took at least two IPTp-SP doses which was associated with 50% reduction of Plasmodium; (P.) falciparum infection in primigravidae. Previous malaria treatment was a risk factor for peripheral P. falciparum infection, while uptake of IPTp-SP was associated with reduced parasitaemia. Anaemia prevalence was 38.0%, low birth weight and prematurity rates were 6.0 and 12.0% respectively. Young age was associated with a higher frequency of malaria, anaemia, low birth weight and preterm delivery (p<0.01). Birth weight significantly rose with increasing age (p<0.01), parity (p=0.03) and number of SP doses (p=0.03). A birth weight reduction of 230 g in case of peripheral parasitaemia (p=0.02) and of 210 g with placental parasitaemia (p=0.13) was observed.

CONCLUSIONS

Microscopic P. falciparum prevalence during pregnancy significantly declined between 2005 and 2011, following IPTp-SP implementation in Gabon. Young women and paucigravidae remain the most susceptible to malaria and associated outcomes.

Inventory of potential vectors of trypanosoma and infection rate of the Tsetse fly in the National Park of Ivindo, Gabon

BACKGROUND

Trypanosoma's vectors distribution is poorly investigated in Gabon, where Trypanosomiasis historical foci exist. Thus, an active detection of Trypanosoma sp transmission needs to be assessed.

OBJECTIVES

The present study aims to identify potential vectors of Trypanosoma sp and to evaluate the infection rate of the Tsetse fly in an area of Gabon.

METHODS

An entomological survey was conducted in the National Park of Ivindo in May 2012 using Vavoua traps. All captured insects were identified. Tsetse were dissected and organs were microscopically observed to detect the presence of Trypanosoma sp.

RESULTS

247 biting flies known as vectors of Trypanosomiasis were caught including 189 tsetse flies, 32 Tabanid and 26 Stomoxys. Tsetse flies had the highest bulk densities per trap per day (ADT = 3 tsetse / trap / day), while the lowest density was found among Stomoxys (ADT= 0.41 Stomoxys / trap / day). The infection rate of flies was 6.3%. Infectious organs were midguts and to a lesser extent salivary glands and proboscis.

CONCLUSION

The presence of Tsetse infected by Trypanosoma highlights an existing risk of trypanosomiasis infection in the National Park of Ivindo.

Effects of prolactin and cortisol on natural killer (NK) cell surface expression and function of human natural cytotoxicity receptors (NKp46, NKp44 and NKp30)

The surface density of the triggering receptors (e.g. NKp46 and NKp30) responsible for natural killer (NK) cell-mediated cytotoxicity determines the ability of NK cells to kill susceptible target cells. In this study, we show that prolactin up-regulates and cortisol down-regulates the surface expression of NKp46 and NKp30. The prolactin-mediated activation and the cortisol-mediated inhibition of natural cytotoxicity receptor (NCR) surface expression reflects gene regulation at the transcriptional level. NKp46 and NKp30 are the major receptors involved in the NK-mediated killing of K562, a human chronic myelogenous leukaemia cell line. Accordingly, the prolactin dramatically increased the NK-mediated killing of the K562 cell line, whereas cortisol abolished this activity. Our data suggest a mechanism by which prolactin activates the lytic function of NK cells, and cortisol inhibits the NK-mediated attack.