DNA Barcode Reference Library for the African Citrus Triozid, Trioza erytreae (Hemiptera: Triozidae): Vector of African Citrus Greening.

Citrus (Citrus spp.) production continues to decline in East Africa, particularly in Kenya and Tanzania, the two major producers in the region. This decline is attributed to pests and diseases including infestation by the African citrus triozid, Trioza erytreae (Del Guercio) (Hemiptera: Triozidae). Besides direct feeding damage by adults and immature stages, T. erytreae is the main vector of 'Candidatus Liberibacter africanus', the causative agent of Greening disease in Africa, closely related to Huanglongbing. This study aimed to generate a novel barcode reference library for T. erytreae in order to use DNA barcoding as a rapid tool for accurate identification of the pest to aid phytosanitary measures. Triozid samples were collected from citrus orchards in Kenya, Tanzania, and South Africa and from alternative host plants. Sequences generated from populations in the study showed very low variability within acceptable ranges of species. All samples analyzed were linked to T. erytreae of GenBank accession number KU517195. Phylogeny of samples in this study and other Trioza reference species was inferred using the Maximum Likelihood method. The phylogenetic tree was paraphyletic with two distinct branches. The first branch had two clusters: 1) cluster of all populations analyzed with GenBank accession of T. erytreae and 2) cluster of all the other GenBank accession of Trioza species analyzed except T. incrustata Percy, 2016 (KT588307.1), T. eugeniae Froggatt (KY294637.1), and T. grallata Percy, 2016 (KT588308.1) that occupied the second branch as outgroups forming sister clade relationships. These results were further substantiated with genetic distance values and principal component analyses.

Cold tolerance and disinfestation of Bactrocera invadens (Diptera: Tephritidae) in 'Hass' avocado.

Bactrocera invadens (Diptera: Tephritidae) has spread rapidly across Africa and currently poses a phytosanitary threat to the fruit industry of South Africa. In reaction a cold mitigating treatment to provide phytosanitary security to importing countries was developed in Nairobi, Kenya. Using laboratory reared fruit flies, the rate of development in 'Hass' avocado (Persea americana Miller) was determined at 28 degrees C. Fruit ripeness or softness was found to be a factor improving larval fruit fly survival. Using this information the egg and larval developmental stages were subjected to 2 degrees C cold treatment and it was found that the third instars were the most cold tolerant life stage and that it was expected that between 16 and 17 d treatment would provide phytosanitary security. There were no survivors in the treatment of an estimated 153,001 individuals in four replicates at an average fruit pulp temperature of 2 degrees C satisfying the Probit 9 level of efficiency at a confidence of >95%. These data provide evidence that a continuous cold treatment of 1.5 degrees C or lower for 18 d would provide phytosanitary security in that any consignment entering an importing country poses no risk of accidental importation of B. invadens.

Cold susceptibility and disinfestation of Bactrocera invadens (Diptera: Tephritidae) in oranges.

To develop a cold disinfestation treatment for the fruit fly Bactrocera invadens Drew, Tsuruta & White (Diptera: Tephritidae) that is rapidly spreading across Africa, research was conducted in Nairobi, Kenya, using flies from a laboratory culture and 'Valencia' orange (Citrus sinensis L. Osbeck) as the host. The developmental rate of B. invadens in Valencia oranges was determined at 28 degrees C, and the third instar was found to be the least susceptible of the egg and larval life stages to cold treatment at 1.1 degrees C in oranges. When 22,449 B. invadens third instars were exposed in oranges to a cold treatment with an approximate midpoint of 1.1 +/- 0.5 degrees C, the results suggested that a period of 16 d would be worthwhile verifying on a larger scale in oranges. Results from the first replicate of 16,617 larvae showed no survivors, but the second replicate of 23,536 larvae had three survivors. Because a longer cold treatment based on a mean temperature of 1.1 degrees C would create logistical difficulties for some export markets, further replicates were conducted at an approximate midpoint of 0.5 degrees C and at mean hourly maximum of 0.9 +/- 0.5 degrees C, for 16 d. After three replicates, in which 65,752 B. invadens third instars in total were treated with no survivors, the Japanese requirement of 99.99% mortality at the 95% confidence level was surpassed. The following treatment protocol for B. invadens larvae in oranges can therefore be recommended: fruit pulp to be maintained at temperatures of 0.9 degrees C or lower for 16 consecutive days.

Field infestation, life history and demographic parameters of the fruit fly Bactrocera invadens (Diptera: Tephritidae) in Africa.

Field infestation rates of an invasive fruit fly species, Bactrocera invadens Drew Tsuruta & White on mango was determined at different localities in Kenya. At most of the locations and especially at low elevations, B. invadens frequently shared the same fruit with the indigenous fruit fly species Ceratitis cosyra (Walker) but often occurred at higher numbers than C. cosyra. The level of infestation varied with location ranging from 3.0 to 97.2 flies per kg of fruit. There was a significant inverse relationship between numbers of flies per kg of fruit and elevation at which fruit was collected, suggesting that B. invadens is a predominantly lowland pest. On an artificial diet, development of B. invadens immatures lasted 25 days; egg incubation required 1.2 days, larval development 11.1 days and puparia-adult development 12.4 days. About 55% of eggs developed to the adult stage. Life expectancy at pupal eclosion was 75.1 days in females and 86.4 days in males. Average net fecundity and net fertility were 794.6 and 608.1 eggs, respectively, while average daily oviposition was 18.2 eggs. Daily population increase was 11% and mean generation time was 31 days. Results are discussed in relation to the biology and ecology of the insect and in the development of mass rearing and control measures for B. invadens.

Prevalence of exercise induced bronchospasm in Kenyan school children: an urban-rural comparison.

BACKGROUND: Higher rates of exercise induced bronchospasm (EIB) have been reported for urban than for rural African schoolchildren. The change from a traditional to a westernized lifestyle has been implicated. This study was undertaken to examine the impact of various features of urban living on the prevalence of EIB in Kenyan school children. METHODS: A total of 1226 children aged 8-17 years attending grade 4 at five randomly selected schools in Nairobi (urban) and five in Muranga district (rural) underwent an exercise challenge test. A respiratory health and home environment questionnaire was also administered to parents/guardians. This report is limited to 1071 children aged < or = 12 years. Prevalence rates of EIB for the two areas were compared and the differences analysed to model the respective contributions of personal characteristics, host and environmental factors implicated in childhood asthma. RESULTS: A fall in forced expiratory volume in one second (FEV1) after exercise of > or = 10% occurred in 22.9% of urban children and 13.2% of rural children (OR 1.96, 95% CI 1.41 to 2.71). The OR decreased to 1.65 (95% CI 1.10 to 2.47) after accounting for age, sex, and host factors (a family history of asthma and breast feeding for less than six months), and to 1.21 (95% CI 0.69 to 2.11) after further adjustment for environmental factors (parental education, use of biomass fuel and kerosene for cooking, and exposure to motor vehicle fumes). CONCLUSIONS: The EIB rates in this study are higher than any other reported for African children, even using more rigorous criteria for EIB. The study findings support a view which is gaining increasing credence that the increase in prevalence of childhood asthma associated with urbanisation is the consequence of various harmful environmental exposures acting on increasingly susceptible populations.

BCG scar survey among primary school children in Kenya (1986-1990).

Bacillus Calmette Guerin (BCG) vaccination is essential in the control of tuberculosis (TB) especially in countries like Kenya where TB is still a public health problem and BCG is given to all children at birth as a matter of policy. The present survey was launched in 1986 to assess both BCG vaccination coverage and to compare its findings with the 1979/81 BCG scar survey results. Using random cluster sampling procedures, all primary school children aged 6-13 years from schools in each of 12 districts were included in the survey. A total of 46357 school children were registered. Of these, 3642 (7.9%) were excluded from the survey for a variety of reasons. Of the remaining 42715 (92.1%) children, 26781 (62.7%) had BCG scars present. Overall there was a significant upward trend of 15% in BCG vaccination coverage in the country. However, in some districts the coverage was found to have fallen quite significantly.

PIP: In 1986-1990, researchers conducted a BCG scar survey in 360 randomly selected primary schools in 12 districts in Kenya to determine BCG vaccination coverage. They used primary schools because more than 70% of all school age children were enrolled in school. They compared this survey's findings with those of the 1979-1981 BCG scar house-to-house survey. The districts included Elgeyo Marakwet, Kakamega, Kilifi, Kisii, Kitui, Siagya, Kwale, Meru, Muranga, Nakuru, Nairobi, and South Nyanza. The ages of the 42,715 healthy children ranged from 6-13 years old. 26,781 (62.7%) children had a BCG scar, indicating that the National Tuberculosis Control Program had not yet reached its target of 70% BCG vaccination coverage. Nairobi had the highest BCG coverage, while Kisii district had the lowest BCG coverage (82.73% vs. 44.01%). BCG coverage decreased as age increased (p .001). For example, 6-year-old males and females had a BCG coverage rate of 64.43% and 62.39%, respectively, while the corresponding figures for 13-year-olds were 52.93% and 49.13%. BCG vaccination coverage increased significantly between the two surveys (an increase of 15%) (60.8% vs. 62.7%; p .01). South Nyanza district experienced the greatest improvement in BCG coverage between the 2 surveys, while Kilifi district experienced the greatest decline in coverage. The greatest upward trend was observed in the Western and Rift Valley provinces, while the greatest downward trend was observed in the Coast and Eastern provinces.