New okra genotypes for the management of aphids (Hemiptera: Aphididae) in the diverse ecological landscapes of Central Africa.

Various aphid species, including Aphis gossypii Glover (Hemiptera: Aphididae), are considered important pests of okra and other vegetables. Previous studies under 1 environment in Cameroon, Central Africa, had found multiple okra genotypes with resistance to A. gossypii. However, the stability and yield performance of the "resistant" genotypes across different environments were unknown. Ten previously identified aphid-resistant okra genotypes along with 1 commercial variety and a local landrace (specific to a given location) were compared during 2 seasons in replicated trials in 4 agro-ecological zones of Cameroon that also represent large areas of Central Africa. Aphid populations and okra yield parameters were evaluated. Breeding values were predicted using a linear mixed model for all data, and genotypes by location interactions were identified. The area under the infestation pressure curve (AUIPC) was calculated using aphid count data and subjected to resistance analysis. The Local-the most susceptible with the highest breeding value (+2.33)-and VI060794-one of the moderately resistant-genotypes had the highest yield per hectare. The only resistant genotype VI036213 had the lowest breeding value (-2.20). Genotype × location interactions were significant for yield, pod width, and plant height, while location variance was significant for all parameters evaluated. When considering that higher aphid densities could lead to greater pesticide use and, therefore higher production and environmental costs, the high-yielding VI060794-with moderate aphid resistance across multiple environments-presents an alternative or substitute for local landraces across multiple agro-ecologies of Cameroon and (by extension) Central Africa.

Grasshopper (Orthoptera: Acridomorpha) diversity in response to fallow-land use in southern Cameroon with recommendations for land management.

The sensitivity of grasshoppers to disturbance makes them useful bioindicators for land management. The current study compared the grasshopper communities of three fallow-lands at different levels of human pressure: heavily used land (Ongot), moderately used land (Zamakoe), and least-used land (Ngutadjap). Grasshoppers were sampled by nets, pitfall traps, and box quadrats. Their species composition was analyzed using species-richness, abundance, abundance distribution-model, occurrence, and diversity indexes. Species number was not very different between localities. However, the opening up of forests by human activities offers suitable environment for the development or proliferation of the pest grasshopper populations such as Zonocerus variegatus (Linnaeus, 1758), Eyprepocnemis plorans (Charpentier, 1825), and Catantops sylvestrisJago, 1984, which are adapted to the very common Asteraceae found in fallow lands. Native forest species [such as Mazaea granulosa Stål, 1876, Holopercna gerstaeckeri (Bolívar, 1890), Digentia fasciataRamme, 1929] were, generally absent or rare and were collected in only forest/fallow-land ecotones. Low abundance and low occurrence of ecotone species fitted the log-normal abundance distribution model. The grasshopper communities of the less degraded localities were quite similar, but different from the Ongot community. Forest management by reforestation, reduction of slash-and-burn agriculture, and wood cutting, would restore the original grasshopper assemblages and general environmental health.

Assessment of Dengue and Chikungunya Infections among Febrile Patients Visiting Four Healthcare Centres in Yaoundé and Dizangué, Cameroon.

Dengue and chikungunya are now widely distributed in Cameroon, but there is still not enough information on their prevalence in different epidemiological settings. This study was undertaken to assess the prevalence of dengue and chikungunya in both urban and rural settings in Cameroon using three diagnostic tools. From December 2019 to September 2021, willing febrile (temperature >38 °C) outpatients visiting four healthcare facilities in the cities of Yaoundé and Dizangué were screened for dengue, and chikungunya. Clinical features of patient were recorded in a form, and their blood samples were analysed using real-time reverse transcriptase-polymerase chain reaction (rtRT-PCR), rapid diagnostic tests (RDTs) and enzyme-linked immuno-sorbent assays (ELISA). Odds ratios were used to determine the level of association between socio-demographic factors, clinical features, and infection status. The Kappa coefficient permitted to assess the level of agreement between RDTs and ELISA. Overall, 301 febrile patients were recruited in the study: 198 in Yaoundé and 103 in Dizangué. The prevalence of infection varied with the diagnostic tool used. For dengue diagnostics, 110 patients were positive to rtRT-PCR: 90 (45.45%) in Yaoundé, and 20 (19.42%) in Dizangué. The prevalence of dengue IgM using ELISA varied from 22.3% in Dizangué to 30.8% in Yaoundé. Dengue IgM rate using RDTs was 7.6% in Yaoundé and 3.9% in Dizangué. For chikungunya, one (0.5%) patient (Yaoundé, suburb) was positive to rtRT-PCR. The prevalence of chikungunya IgM according to ELISA varied from 18.4% in Dizangué to 21.7% in Yaoundé, while it was 4.5% in Yaoundé and 12.6% in Dizangué with RDTs. Only abdominal and retro-orbital pains were significantly associated with acute dengue infection. All four dengue serotypes were recorded, with a predominance of DENV-3 (35.45%) and DENV-4 (25.45%). Rapid Diagnostic Tests for either chikungunya or dengue displayed very poor sensitivity. This study further confirms the high endemicity of both dengue and chikungunya in Yaoundé and Dizangué. These data stress the need for active surveillance and the implementation of vector control measures to prevent the occurrence of outbreaks across the country.

Insights into factors sustaining persistence of high malaria transmission in forested areas of sub-Saharan Africa: the case of Mvoua, South Cameroon.

BACKGROUND: In Mvoua, a village situated in a forested area of Cameroon, recent studies have reported high prevalence of Plasmodium falciparum infection among the population. In order to understand factors that can sustain such a high malaria transmission, we investigated the biology of Anopheles vectors and its susceptibility to insecticides, as well as long-lasting insecticidal net (LLIN) coverage, use and bio-efficacy. METHODS: A longitudinal entomological survey was conducted from July 2018 to April 2019. Adult mosquitoes were collected using the human landing catch (HLC) method and identified using morphological and molecular techniques. Anopheles gambiae (s.l.) larvae were sampled from several stagnant water pools throughout the village and reared to generate F1 adults. The presence of P. falciparum circumsporozoite antigen was detected in the heads and thoraces of mosquitoes collected as adults using an enzyme-linked immunosorbent assay. The insecticide susceptibility status of the local An. gambiae (s.l.) F1 population to the pyrethroid insecticides deltamethrin 0.5% and permethrin 0.75% was determined using World Health Organization-tube bioassays, while the frequency of the knockdown resistance (kdr) mutation was determined by PCR. Coverage, use and physical integrity of LLINs were assessed in households, then cone assays were used to test for their bio-efficacy on both the reference insecticide-susceptible Kisumu strain and on field F1 An. gambiae (s.l.) RESULTS: In total, 110 Anopheles mosquitoes were collected, of which 59.1% were identified as Anopheles funestus (s.l.), 38.18% as An. gambiae (s.l.) and 2.72% as An. ziemanii. Anopheles funestus was the most abundant species except in the long rainy season, when An. gambiae (s.l.) predominated (65.8%). In the dry seasons, vectors were principally endophagous (76% of those collected indoors) while they tended to be exophagous (66% of those collected outdoors) in rainy seasons. High Plasmodium infection was observed in An. gambiae (s.l.) and An. funestus, with a circumsporozoitic rate of 14.29 and 10.77%, respectively. Anopheles gambiae (s.l.) was highly resistant to pyrethroid insecticides (mortality rates: 32% for permethrin and 5% for deltamethrin) and harbored the kdr-L1014F mutation at a high frequency (89.74%). Of the 80 households surveyed, only 47.69% had achieved universal coverage with LLNs. Around 70% of the LLINs sampled were in poor physical condition, with a proportionate hole index > 300. Of the ten LLNs tested, eight were effective against the An. gambiae reference insecticide-susceptible Kisumu strain, showing mortality rate of > 80%, while none of these LLINs were efficient against local An. gamabie (s.l.) populations (mortality rates < 11.5%). CONCLUSION: A combination of elevated P. falciparum infection in Anopheles vector populations, insufficient coverage and loss of effectiveness of LLINs due to physical degradation, as well as high resistance to pyrethroid insecticides is responsible for the persistence of high malaria transmission in forested rural area of Mvoua, Cameroon.

Monogenean fauna of alien tilapias (Cichlidae) in south China.

Tilapias are important aquaculture fishes that have been introduced widely all over the world, often carrying their monogenean parasites with them. An extensive investigation on monogeneans of invasive tilapias was conducted in 19 natural water sources in south China between July 2015 and December 2017. We found nine known species of monogeneans, i.e., Enterogyrus coronatus, E. malmbergi, Cichlidogyrus cirratus, C. halli, C. sclerosus, C. thurstonae, C. tilapiae, Scutogyrus longicornis, Gyrodactylus cichlidarum, and one unknown Gyrodactylus species. In addition to reporting ten new hosts and four new geographical records, we observed new morphological characteristics of these species. Observation on living specimens of Enterogyrus spp. demonstrated that these two species have characteristic opisthaptoral retraction capacities, while the opisthaptor glands were not observed in our specimens of E. coronatus and E. malmbergi. The morphological differences of the accessory piece of the male copulatory complex between C. cirratus and C. mbirizei (character for species differentiation) could result from the observation at different perspectives, which indicates that C. mbirizei is likely a synonym of C. cirratus. A more detailed structure of the sclerotized parts of Cichlidogyrus spp. and S. longicornis were revealed by scanning electron microscopy. As was the case for the monogeneans found on alien tilapias from other geographic regions, the present study confirmed the high potential of these monogeneans to establish populations in new habitats.

HIV Drug Resistance Testing in a Resource Limited Setting with High Viral Diversity: The First Twenty Eight Months Experience.

BACKGROUND: First line antiretroviral therapy in a resource-limited setting consists of nucleotide and non-nucleotide reverse transcriptase inhibitors. Protease inhibitors are the hub of second line therapy. The decision to change antiretroviral therapy for a patient is frequently presumptive because of the lack of genotypic resistance tests in routine follow-up. We describe here the resistance profiles observed in patients with varying terms of antiretroviral therapy in Cameroon after implementation of HIV genotypic resistance testing in routine practice. METHODS: HIV genotypic resistance testing was carried out on consecutive samples received between August 2013 and November 2015. Protease (Prot) and reverse transcriptase (Rt) genes of the HIV genome were amplified, sequenced and analyzed for drug resistance mutations following the algorithm set up by the French National Agency for research on HIV/AIDS and viral hepatitis. RESULTS: Specimens from a total of 167 patients infected with non-B HIV subtypes were received during the study period. Overall 61.7% patients had viral loads of more than 3log copies/ml, suggesting treatment failure. Among the 72 patients on first line, 56 (77.8%) were resistant to Lamivudine, 57 (79.1%) to Efavirenz and 58 (80.6%) to Nevirapine. Overall, more patients (75.0%) on first line antiretroviral therapy harbored multi-drug resistance compared to their counterparts on second line (25.8%). CONCLUSION: This study revealed that a group of patients with antiretroviral therapy failure harbored multi-drug resistance mutations related to the majority of drugs in the first line regimen. Therefore, HIV resistance testing could be a useful tool to improve HIV care in resource limited settings like Cameroon where treatment options are limited.

Patterns of species richness and diversity of insects associated with cucurbit fruits in the southern part of Cameroon.

Patterns of species diversity and community structure of insects associated with fruits of domesticated cucurbits were investigated from January 2009 to 2011 in three localities from two agroecological zones in the southern part of Cameroon. Rarefaction curves combined with nonparametric estimators of species richness were used to extrapolate species richness beyond our own data. Sampling efforts of over 92% were reached in each of the three study localities. Data collected revealed a total of 66 insect morphospecies belonging to 37 families and five orders, identified from a set of 57,510 insects. The orders Diptera (especially Tephritidae and Lonchaeidae) and Hymenoptera (mainly Braconidae and Eulophidae) were the most important, in terms of both abundance and species richness on the one hand, and effects on agronomic performance on the other. Values for both the species diversity (Shannon and Simpson) and the species richness indices (Margalef and Berger-Parker) calculated showed that the insect communities were species-rich but dominated, all to a similar extent, by five main species (including four fruit fly species and one parasitoid). Species abundance distributions in these communities ranged from the Zipf-Mandelbrot to Mandelbrot models. The communities are structured as tritrophic networks, including cucurbit fruits, fruit-feeding species (fruit flies) and carnivorous species (parasitoids). Within the guild of the parasitoids, about 30% of species, despite their low abundance, may potentially be of use in biological control of important pests. Our field data contribute in important ways to basic knowledge of biodiversity patterns in agrosystems and constitute baseline data for the planned implementation of biological control in Integrated Pest Management.

Intestinal parasitic and candida infection associated with HIV infection in Cameroon.

INTRODUCTION: HIV causes progressive impairment of the cellular immune system leading to increased susceptibility to infectious agents. Parasitic infestations are common in HIV-infected patients and usually lead to diarrhoea. Few studies have addressed the issue of intestinal parasites among HIV-infected persons in Cameroon.  This investigation was conducted in Douala, Cameroon, to assess the prevalence of gastrointestinal parasites in HIV-infected patients, taking into account their immune status and treatment course. METHODOLOGY: Stool and blood samples were collected from 201 HIV-positive patients for the investigation of intestinal pathogens and CD4+ counts. RESULTS: Fifty-six (27.9%) patients harbored pathogens. The most frequent pathogens were Candida spp. (14.9%), Cryptosporidium spp. (7.5%), Entamoeba histolytica, and Entamoeba dispar (3%). The presence of pathogens was significantly associated with diarrhoea, as they were found in 48.6% of diarrhoeic stools and 23.2% of non-diarrhoeic stools (OR = 3.14, p= 0.0018). Prevalence of pathogens and diarrhoea were significantly higher in patients with CD4+ counts ≤ 200 cells/µL (OR = 2.17, p = 0.0349 and OR = 8.46, p = 0.000019 respectively). CONCLUSIONS: This study highlights the need for investigating intestinal pathogens in HIV-infected patients presenting with diarrhoea, especially when their CD4+ counts are low.