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Biocontrol of Culex quinquefasciatus using the insect parasitic nematode, Romanomermis iyengari (Nematoda: Mermithidae)

Abagli AZ, Alavo TBC

Trop Biomed, 2019 Dec 01;36(4):1003-1013.
PMID: 33597470

Cx. quinquefasciatus is a common nuisance mosquito widely distributed in tropical and subtropical areas. This mosquito is also a vector of urban filariasis. Control with chemicals has been hampered by the development of resistance against chemical insecticides and rising problems of environmental contamination associated with them. Therefore, it is important to adopt more integrated mosquito management approaches that include sustainable, non chemical solutions. The mermithid nematode Romanomermis iyengari is one of several natural control alternatives to synthetic pesticides for mosquito suppression. This study evaluated the effectiveness of the nematode R. iyengari for control of Cx. quinquefasciatus. The nematode R. iyengari was mass-produced, and pre-parasitics (J2) were used for laboratory and field experiments. In laboratory experiments, two concentrations of pre-parasitics (5 and 10 J2 per larva) were tested against L1, L2 and L3 instars larvae of Cx. quinquefasciatus. Infected larvae were observed daily to determine their mortality rate and the number of postparasitic nematodes emerging from dead larvae. In field experiments, 1000, 2000 and 3000 J2/m2 were sprayed in separate natural Cx. quinquefasciatus breeding sites. After treatment, the larval mosquito density in the breeding sites was assessed every 5 days. Laboratory results showed that all tested Cx. quinquefasciatus instars larvae were susceptible to nematode infection. The mortality rates observed for each larval stage indicated that the concentration of 10 J2 kills larvae faster, and that the L1 larvae died earlier than older larvae. The average number of post-parasitic nematodes emerging per larva increases with increasing nematode concentration; also more post-parasitic nematodes emerged from the L2 larvae. Field data showed that, in breeding site treated with 3000 J2 per square meter, larval mosquito reduction reached 97% after nematode application. The dosage of 1000 J2 per square meter did not reduce the larval density. The insect parasitic nematode R. iyengari could be easily used as component of integrated mosquitoes control program in lymphatic filariasis endemic countries.

Matched MeSH terms: Benin
Variations des caractéristiques des huiles de palme et notamment de leurs caroténoides

Bienaymé A, Servant M

Qualitas Plantarum et Materiae Vegetabiles, 1958;3-4:336-353.
DOI: 10.1007/BF01884062

During two years the authors have assembled monthly analytical data of oilpalms, from 15 different stations. The determinations spread as far as the French, Portuguese and Spanish territory in Africa and British Malaya also. The following analyses were carried out: iodine number, titer point, melting point and the carotenoids of these oils, according to origine, race and time of gathering. As to iodine number and amount of carotenoid, the race is decisive for these data; the oils from the natural stock of the Ivory Coast have a higher iodine number (57-60). The oils from the natural stock of Togo, Dahomey, Portuguese and French Guinea are richer in carotene (up to 0.16, even 0.19%) with medium iodine number (54-56). The oils from the industrial plantations, with selected trees of the race Dura-Deli, from the Far East as well as from the Ivory Coast, have lower iodine numbers (52-53) and are poor in carotene (0.05). South of the equator in Africa, all analysed races of oil palms had a lower iodine number (53-55) and were poor in carotene (0.05). During one year the amount of carotene fluctuates about one third of its maximum; this maximum is rather striking in Togo and Dahomey; it is to be found from January to May; period of high production of the oil in the Palm groves, e.g. in the dry season with warm climate and good insolation. Heavy rain-showers effect a rapid decrease of the contents of carotene after six weeks (duration of the formation of the fruit). Furthermore, the residual oils (extracted by solvents) were analysed; they are 2 to 3 times richer in carotenoids than the common palm oil; but the contents of β-carotene seems somewhat lower. The authors think it possible to find exactly defined uses for the different oils. © 1958 Uitgeverij Dr. W. Junk.

Matched MeSH terms: Benin
Fulltext The impact of delayed treatment of uncomplicated P. falciparum malaria on progression to severe malaria: A systematic review and a pooled multicentre individual-patient meta-analysis

Mousa A, Al-Taiar A, Anstey NM, Badaut C, Barber BE, Bassat Q, et al.

PLoS Med, 2020 Oct;17(10):e1003359.
PMID: 33075101 DOI: 10.1371/journal.pmed.1003359

BACKGROUND: Delay in receiving treatment for uncomplicated malaria (UM) is often reported to increase the risk of developing severe malaria (SM), but access to treatment remains low in most high-burden areas. Understanding the contribution of treatment delay on progression to severe disease is critical to determine how quickly patients need to receive treatment and to quantify the impact of widely implemented treatment interventions, such as 'test-and-treat' policies administered by community health workers (CHWs). We conducted a pooled individual-participant meta-analysis to estimate the association between treatment delay and presenting with SM.
METHODS AND FINDINGS: A search using Ovid MEDLINE and Embase was initially conducted to identify studies on severe Plasmodium falciparum malaria that included information on treatment delay, such as fever duration (inception to 22nd September 2017). Studies identified included 5 case-control and 8 other observational clinical studies of SM and UM cases. Risk of bias was assessed using the Newcastle-Ottawa scale, and all studies were ranked as 'Good', scoring ≥7/10. Individual-patient data (IPD) were pooled from 13 studies of 3,989 (94.1% aged <15 years) SM patients and 5,780 (79.6% aged <15 years) UM cases in Benin, Malaysia, Mozambique, Tanzania, The Gambia, Uganda, Yemen, and Zambia. Definitions of SM were standardised across studies to compare treatment delay in patients with UM and different SM phenotypes using age-adjusted mixed-effects regression. The odds of any SM phenotype were significantly higher in children with longer delays between initial symptoms and arrival at the health facility (odds ratio [OR] = 1.33, 95% CI: 1.07-1.64 for a delay of >24 hours versus ≤24 hours; p = 0.009). Reported illness duration was a strong predictor of presenting with severe malarial anaemia (SMA) in children, with an OR of 2.79 (95% CI:1.92-4.06; p < 0.001) for a delay of 2-3 days and 5.46 (95% CI: 3.49-8.53; p < 0.001) for a delay of >7 days, compared with receiving treatment within 24 hours from symptom onset. We estimate that 42.8% of childhood SMA cases and 48.5% of adult SMA cases in the study areas would have been averted if all individuals were able to access treatment within the first day of symptom onset, if the association is fully causal. In studies specifically recording onset of nonsevere symptoms, long treatment delay was moderately associated with other SM phenotypes (OR [95% CI] >3 to ≤4 days versus ≤24 hours: cerebral malaria [CM] = 2.42 [1.24-4.72], p = 0.01; respiratory distress syndrome [RDS] = 4.09 [1.70-9.82], p = 0.002). In addition to unmeasured confounding, which is commonly present in observational studies, a key limitation is that many severe cases and deaths occur outside healthcare facilities in endemic countries, where the effect of delayed or no treatment is difficult to quantify.
CONCLUSIONS: Our results quantify the relationship between rapid access to treatment and reduced risk of severe disease, which was particularly strong for SMA. There was some evidence to suggest that progression to other severe phenotypes may also be prevented by prompt treatment, though the association was not as strong, which may be explained by potential selection bias, sample size issues, or a difference in underlying pathology. These findings may help assess the impact of interventions that improve access to treatment.

Matched MeSH terms: Benin/epidemiology
Fulltext Differences in virulence and immune response induced in a murine model by isolates of Mycobacterium ulcerans from different geographic areas

Ortiz RH, Leon DA, Estevez HO, Martin A, Herrera JL, Romo LF, et al.

Clin Exp Immunol, 2009 Aug;157(2):271-81.
PMID: 19604267 DOI: 10.1111/j.1365-2249.2009.03941.x

Buruli ulcer (BU) is the third most common mycobacterial disease in immunocompetent hosts. BU is caused by Mycobacterium ulcerans, which produces skin ulcers and necrosis at the site of infection. The principal virulence factor of M. ulcerans is a polyketide-derived macrolide named mycolactone, which has cytotoxic and immunosuppressive activities. We determined the severity of inflammation, histopathology and bacillary loads in the subcutaneous footpad tissue of BALB/c mice infected with 11 different M. ulcerans isolates from diverse geographical areas. Strains from Africa (Benin, Ghana, Ivory Coast) induced the highest inflammation, necrosis and bacillary loads, whereas the strains collected from Australia, Asia (Japan, Malaysia, New Guinea), Europe (France) and America (Mexico) induced mild inflammation. Subsequently, animals were infected with the strain that exhibited the highest (Benin) or lowest (Mexico) level of virulence in order to analyse the local immune response generated. The Mexican strain, which does not produce mycolactone, induced a predominantly T helper type 1 (Th1) cytokine profile with constant high expression of the anti-microbial peptides beta defensins 3 and 4, in co-existence with low expression of the anti-inflammatory cytokines interleukin (IL)-10, IL-4 and transforming growth factor (TGF)-beta. The highly virulent strain from Benin which produces mycolactone A/B induced the opposite pattern. Thus, different local immune responses were found depending on the infecting M. ulcerans strain.

Matched MeSH terms: Benin