Surviving Sengstaken.

AIM OF THE STUDY: To report the outcomes of children who underwent Sengstaken-Blakemore tube (SBT) insertion for life-threatening haemetemesis. METHODS: Single institution retrospective review (1997-2012) of children managed with SBT insertion. Patient demographics, diagnosis and outcomes were noted. Data are expressed as median (range). MAIN RESULTS: 19 children [10 male, age 1 (0.4-16) yr] were identified; 18 had gastro-oesophageal varices and 1 aorto-oesophageal fistula. Varices were secondary to: biliary atresia (n=8), portal vein thrombosis (n=5), alpha-1-anti-trypsin deficiency (n=1), cystic fibrosis (n=1), intrahepatic cholestasis (n=1), sclerosing cholangitis (n=1) and nodular hyperplasia with arterio-portal shunt (n=1). Three children deteriorated rapidly and did not survive to have post-SBT endoscopy. The child with an aortooesophageal fistula underwent aortic stent insertion and subsequently oesophageal replacement. Complications included gastric mucosal ulceration (n=3, 16%), pressure necrosis at lips and cheeks (n=6, 31%) and SBT dislodgment (n=1, 6%). Six (31%) children died. The remaining 13 have been followed up for 62 (2-165) months; five required liver transplantation, two underwent a mesocaval shunt procedure and 6 have completed endoscopic variceal obliteration and are under surveillance. CONCLUSIONS: SBT can be an effective, albeit temporary, life-saving manoeuvre in children with catastrophic haematemesis.

New enzymatic assay, parasite lactate dehydrogenase, in diagnosis of malaria in Kenya.

BACKGROUND: The unique ability of plasmodial lactate dehydrogenase p(LDH) to utilise 3-acetyl pyridine dinucleotide (APAD) in lieu of NAD as a coenzyme in the conversion of pyruvate to lactate, led to the development of a biochemical assay for the detection of plasmodial parasitaemia. Researchers have reported that p(LDH) activity of plasmodia could be used as an assessment of parasitaemia since human red blood cells do not utilise APAD in the metabolism of glucose. OBJECTIVE: To use p(LDH) for field and clinical diagnosis of malaria in endemic regions of Kenya. DESIGN: Prospective field and clinical study. SETTING: Kisumu District Hospital and Walter Reed malaria laboratory in Kenya. SUBJECTS: The study subjects were of three different categories: the healthy non-infected individuals staying out of malaria endemic region (controls group 1), the nonparasitaemic and parasitaemic non- symptomatic healthy individuals living in endemic region {both field study group 2}, the non-parasitaemic and parasitaemic symptomatic individuals living in endemic region {both clinical study group 3}. RESULTS: In the clinical studies, thin smear microscopy gave the highest sensitivity as 75.6% for plasma, while the highest specificity was 71.4%. For red blood cells, the highest sensitivity was 78.4% while specificity was 80%. In the field trials, the highest sensitivity was 89% using thin smear microscopy whereas the specificity was 45% for plasma cut off using thick smear. For red blood cells, the highest sensitivity was 79% while specificity was 66.7%. CONCLUSION: The variations in sensitivity and specificity of this assay in comparison to microscopy is a strong indication that p(LDH) may be measuring even the sequestered parasites that cannot be visualised by microscopy. The results of this study validates the use of p(LDH) as an alternative objective test for malaria diagnosis against microscopy.

Parasite lactate dehydrogenase assay for the determination of antimalarial drug susceptibility of Kenyan field isolates.

BACKGROUND: Researchers have reported that parasite lactate dehydrogenase p(LDH) could be used to determine chemo-sensitivity of plasmodia to compounds with known or presumed antimalarial activities. OBJECTIVE: To determine the drug sensitivity profiles of field adopted malaria isolates from Kisumu using p(LDH) instead of hapoxanthine assay. DESIGN: Prospective field and laboratory study. SETTING: Walter Reed, KEMRI malaria laboratory (Nairobi) and Kisumu District Hospital. SUBJECTS: Twelve field laboratory adopted isolates from Kisumu, five laboratory adopted isolates from other regions in Africa and three reference strains from Walter Reed army Institute of Research, Washington, DC. RESULTS: The p(LDH) enzyme assay was successfully used to measure the IC50 of six antimalarial drugs, chloroquine, quinine, mefloquine, dehydroartemisinin, atovaquone and halofantrine but was not successful with the four other antimalarial drugs, doxycycline, azithromycin, pyrimethamine and sulphadoxine. The Kisumu isolates tested were resistant to chloroquine and mefloquine but sensitive to quinine and the new antimalarial drugs, atovaquone, halofantrine and dehydroartemisinin. CONCLUSION: The non-radioactive p(LDH) can be used for the determination of drug sensitivity to Kenyan field isolates. It is more suited for use in a resource limited environment and may lead to more judicious prescription of new and more expensive antimalarial drugs and mitigate against the rapid spread of multi-drug resistant parasites in the East African region.

Behavioural determinants of gene flow in malaria vector populations: Anopheles gambiae males select large females as mates.

BACKGROUND: Plasmodium-refractory mosquitoes are being rapidly developed for malaria control but will only succeed if they can successfully compete for mates when released into the wild. Pre-copulatory behavioural traits maintain genetic population structure in wild mosquito populations and mating barriers have foiled previous attempts to control malaria vectors through sterile male release. METHODS: Varying numbers of virgin male and female Anopheles gambiae Giles, from two strains of different innate sizes, were allowed to mate under standardized conditions in laboratory cages, following which, the insemination status, oviposition success and egg batch size of each female was assessed. The influence of male and female numbers, strain combination and female size were determined using logistic regression, correlation analysis and a simple mechanistic model of male competition for females. RESULTS: Male An. gambiae select females on the basis of size because of much greater fecundity among large females. Even under conditions where large numbers of males must compete for a smaller number of females, the largest females are more likely to become inseminated, to successfully oviposit and to produce large egg batches. CONCLUSIONS: Sexual selection, on the basis of size, could either promote or limit the spread of malaria-refractory genes into wild populations and needs to be considered in the continued development and eventual release of transgenic vectors. Fundamental studies of behavioural ecology in malaria vectors such as An. gambiae can have important implications for malaria control and should be prioritised for more extensive investigation in the future.

Spatial and temporal distribution of tsetse fly trap catches at Nguruman, southwest Kenya.

Spatial and temporal dynamics of rapidly growing populations of tsetse flies at Nguruman, southwest Kenya during 1993-1995, were investigated, following six years of intensive population suppression with traps over a c. 100 km2 area. The two tsetse species present were randomly distributed in the short rainy season, but were aggregated in the dry and long rainy seasons. Maximum temperature was the dominant weather factor associated with the degree of aggregation. Trends in catches at 20 fixed sites along an 18 km north-south axis were weakly correlated between locations, possibly representing population sub-structuring. In particular, trends in population change were poorly correlated between the area with a long history of trapping suppression in the south and the area with a more recent history of suppression in the north. On a micro-geographic scale, correlations among paired trap catches were clearly related to geographical proximity for Glossina pallidipes Austen (r2 = 0.55); whereas this relationship was quite weak for Glossina longipennis Corti (r2 = 0.12). Positive correlations among trap catches were significant for sites separated by less than c. 3.8 km (G. pallidipes) or 4.8 km (G. longipennis). These results suggest the existence of different population substructures in the two species on a relatively small geographic scale.

Acquisition of resistance to the tick Amblyomma variegatum in Boran cattle, Bos indicus and the effects of Trypanosoma congolense and Babesia bigemina on host resistance.

Resistance was induced in cattle to the tick Amblyomma variegatum by five consecutive infestations with nymphs and adults. Using the principal component analysis (PCA), it was found that percentage of adults engorged, percentage of adults which died, percentage of nymphs which engorged, percentage of nymphs which moulted and percentage of nymphs which died, were the main indicators of resistance against A. variegatum. The percentages of nymphs which engorged or moulted after the third infestation were significantly (P < 0.01) reduced while the percentage of nymphs which died increased significantly (P < 0.01) after the third infestation. Percentages of adults which engorged or died started to decrease significantly (P < 0.01) from the fourth infestation after an initial increase during this period. The acquisition of resistance by cattle to the adult ticks was slower than to the nymphs. Infection of cattle with Trypanosoma congolense and Babesia bigemina after the fifth infestation enhanced the acquired immunity as revealed by the significantly (P < 0.01) increased feeding period of the adult ticks and changes in other parameters.

Choice of resting sites by Anopheles gambiae (Diptera: Culici) in Mwea Rice Irrigation Scheme, Kirinyaga District, Kenya.

Investigations on Anopheles gambiae were carried out in Mwea Rice Irrigation Scheme, Kenya, to determine their preference for resting on various colours of fabrics and bare walls inside rural houses. The inside wall surface of each house was divided into upper, middle and lower sections and the section further partitioned into subsections measuring 0.6 x 0.3m. Two sets of experiments were conducted: one in which the walls were partly fitted with one colour of fabric at a time (double-choice situation), while in the other the walls were fitted with a combination of six colours (red, black, yellow, white, green and blue) of fabric at once, (multiple-choice situation). The number of mosquitoes resting on each of the pieces of cloth pinned to the walls and the uncovered subsections of the wall were recorded for each section of the wall after 24 hours. The results showed resting preference for cloth covered parts of the walls. The white colour was found to best attract mosquitoes followed by colours red, yellow, black, blue and green. The hanging strips in the middle of the houses had fewer mosquitoes resting on them than those on the wall.