Incidence Of Helminth Infections Research Articles

Glucose-6-phosphate dehydrogenase deficiency and the risk of malaria and other diseases in children in Kenya: a case-control and a cohort study

SummaryBackgroundThe global prevalence of X-linked glucose-6-phosphate dehydrogenase (G6PD) deficiency is thought to be a result of selection by malaria, but epidemiological studies have yielded confusing results. We investigated the relationships between G6PD deficiency and both malaria and non-malarial illnesses among children in Kenya.MethodsWe did this study in Kilifi County, Kenya, where the G6PD c.202T allele is the only significant cause of G6PD deficiency. We tested the associations between G6PD deficiency and severe and complicated Plasmodium falciparum malaria through a case-control study of 2220 case and 3940 control children. Cases were children aged younger than 14 years, who visited the high dependency ward of Kilifi County Hospital with severe malaria between March 1, 1998, and Feb 28, 2010. Controls were children aged between 3–12 months who were born within the same study area between August 2006, and September 2010. We assessed the association between G6PD deficiency and both uncomplicated malaria and other common diseases of childhood in a cohort study of 752 children aged younger than 10 years. Participants of this study were recruited from a representative sample of households within the Ngerenya and Chonyi areas of Kilifi County between Aug 1, 1998, and July 31, 2001. The primary outcome measure for the case-control study was the odds ratio for hospital admission with severe malaria (computed by logistic regression) while for the cohort study it was the incidence rate ratio for uncomplicated malaria and non-malaria illnesses (computed by Poisson regression), by G6PD deficiency category.Findings2863 (73%) children in the control group versus 1643 (74%) in the case group had the G6PD normal genotype, 639 (16%) versus 306 (14%) were girls heterozygous for G6PD c.202T, and 438 (11%) versus 271 (12%) children were either homozygous girls or hemizygous boys. Compared with boys and girls without G6PD deficiency, we found significant protection from severe malaria (odds ratio [OR] 0·82, 95% CI 0·70–0·97; p=0·020) among G6PD c.202T heterozygous girls but no evidence for protection among G6PD c.202T hemizygous boys and homozygous girls (OR 1·18, 0·99–1·40; p=0·056). Median follow-up for the mild disease cohort study was 2·24 years (IQR 2·22–2·85). G6PD c.202T had no effect on other common diseases of childhood in heterozygous girls (incidence rate ratio 0·98, 95% CI 0·86–1·11; p=0·82) or homozygous girls or hemizygous boys (0·93, 0·82–1·04; p=0·25), with the sole exception of a marginally significant increase in the incidence of helminth infections among heterozygous girls.InterpretationHeterozygous girls might be the driving force for the positive selection of G6PD deficiency alleles. Further studies are needed to definitively establish the mechanisms by which G6PD deficiency confers an advantage against malaria in heterozygous individuals. Such studies could lead to the development of new treatments.FundingWellcome Trust, UK Medical Research Council, European Union, and Foundation for the National Institutes of Health (as part of the Bill & Melinda Gates Grand Challenges in Global Health Initiative).

Gastrointestinal Helminths from Turkeys in Southeastern United States

Viscera from 390 wild turkeys (Meleagris gallopavo) from 31 collection areas in 10 southeastern states, from 76 pen-raised wild turkeys from Beaufort County, South Carolina, and from 68 domestic turkeys from 7 farm areas located in the states of Florida, Virginia, and West Virginia were examined for helminths. Species of helminths and infection percentages of wild turkeys (=W), penraised wild turkeys (=P), and domestic turkeys (=D) follow: TREMATODA-Brachylaema virginiana 4.4 percent (W); Cotylurus flabelliformis 4.4 percent (W); Echinoparyphium recurvatum 7.2 percent (W); Zygocotyle lunata 1.8 percent (W). CESTODA-Davainea meleagridis 11 percent (W); Hymenolepis cantaniana 4.1 percent (W), 1.5 (D); Hymenolepis carioca 10.5 percent (W), 7.9 (P), 1.5 (D); Metroliasthes lucida 43.1 percent (W); Raillietina georgiensis 6.2 percent (W), 18.4 (P); Raillietina ransomi 12.6 percent (W), 6.6 (P), 2.9 (D); Raillietina williamsi 39.0 percent (W), 27.6 (P); Hymenolepid 2.6 percent (W). NEMATODA--Ascaridia dissimilis 66.2 percent (W), 71.1 (P), 35.3 (D); Ascaridia galli 1.5 percent (W), 3.9 (P), 17.6 (D); Capillaria bursata 1.3 percent (W), 3.9 (P); Capillaria obsignata 9.7 percent (W), 73.7 (P), 14.7 (D); Heterakis gallinae 62.3 percent (W), 53.9 (P), 36.8 (D); Strongyloides avium 0.3 percent (W); Strongyloides sp. 0.5 percent (W); Trichostrongylus tenuis 5.1 percent (W), 6.6 (P). The following nematodes were reported present in one or more birds: Capillaria annulata (W); Dispharynx nasuta (W) and (P); Gongylonema ingluvicola (W) and (P); Seurocyrnea colini (W) and (P); Seurocyrnea sp. (W) and (P). The two flukes (Brachylaema virginiana and Cotylurus flabelliformis) collected from wild turkeys constituted new host records. Numerous new state records of turkey helminths were established. The high percentage of Capillaria obsignata in pen-raised birds indicates the danger of introducing these birds to new locations. The high infectivity rates of all groups with Heterakis gallinae should not be overlooked because the ova of the cecal worm transmit the etiological agent (Histomonas meleagridis) of blackhead. Information on the geographic distribution and incidence of gastrointestinal helminth infections of wild and pen-raised wild turkeys is limited. In an effort to correct this deficiency, a survey of parasitism in turkeys was conducted, and the findings were compared with a similar study on domestic turkeys. Gardiner and Wehr (1949), Mosby and Handley (1943), and Self and Bouchard (1950) have published limited reports on the incidence of helminth infections among wild turkeys. The interrelationships of parasitism among wild, pen-reared wild, and domestic birds have not been established: for instance, Reid and Nugara (1961) found substantial evidence that a new cestode species (the tapeworm Raillietina georgiensis) had been introduced into a flock of domestic turkeys by penraised wild birds from Fitzgerald, Georgia. This study was partially financed by a National Science Foundation Grant (No. G-12999), by the Southeastern Association of Game and Fish Commissioners, and by the U. S. Fish and Wildlife Service (Region 4). The present report has been condensed from a thesis submitted by the senior author in partial fulfillment of the M.S. degree. For procuring viscera of wild and penraised wild turkeys, specific appreciation is expressed to biologists of the game and fish agencies of Alabama, Arkansas, Florida, 1 Journal series paper No. 262, College Experiment Station, University of Georgia, Athens. 2 Present address: Director, Poultry Diagnostic Laboratory, Charles Pfizer & Company, Inc., Cullman, Alabama.