Articles: Department of Biological Sciences

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Nematode diversity and its association with soil properties in monocrop pigeon pea
(Elsevier Ltd, 202-07-03) Maina, Samuel; Karuri, Hannah; Mugweru, Julius
Pigeon pea is a versatile pulse crop grown in semi-arid regions of Kenya; however, its production is affected by plant-parasitic nematodes. The current study was undertaken to investigate the diversity of nematodes and the influence of soil properties on their diversity in monocrop pigeon pea fields in Mbeere North, Embu County, Kenya. Soil samples were collected from Gatunguru B, Gwakaithi, Itururi, Kambungu, Kanyueri, Karigiri, Mbangua and Njarange regions. From each field, soil samples were collected from a depth of 25 cm using W- shaped sampling pattern. The nematodes were identified to the genus level using morphological features. In total, 46 nematode genera assigned to five trophic levels were identified across the eight regions. Abundance of Meloidogyne, Rotylenchulus, Longidorus, Acrobeloides, Cervidellus, Panagrolaimus, Prismatolaimus and Wilsonema varied markedly among the eight regions. Bacterivores belonging to colonizer-persister group 2 were the most prevalent group. There were no differences in Pielou’s evenness, genus richness, Shannon and Simpson diversity indices across the regions. Canonical correspondence analysis indicated significant correlations between certain nematode genera and soil attributes with the first two axes accounting for 56.65% of the variance. Acrobeloides correlated positively with Mg, C, Mn and N, and negatively with Fe. The occurrence of Hoplolaimus and Meso- rhabditis was associated negatively with soil pH, clay and Ca, and positively with sand. The present work reveals a high abundance of economically important PPN in monocrop pigeon pea which necessitates that appropriate nematode management programs are implemented.
Urinary Schistosomiasis in two family populations, using school children as tracers
(1988) Anigbo, E.U.; Nwaorgu, O.C.
Two groups of families designated A and B were studied for Schistosoma haematobium infection in Amagunze, Anambra State, Nigeria. The groups were selected on the basis of a preliminary screening of schoolchildren: group A were children with negative urine samples and group B were those with positive samples. Each group contained 60 children and the families of each of these were screened for schistosomiasis. The total prevalence among the 1017 individuals examined was 48.4% and the mean egg count was 72/10 ml urine. The peak prevalence (73%) and intensity of infection (84 eggs/10 ml of urine) occurred between the ages of 5 and 14 years. The prevalence and intensity of S. haematobium infection was statistically higher in males than in females. Although water contact patterns were similar, families in group B were significantly more infected (59%) than those in group A (36%).
Photolabelling of Prostaglandin E2 receptor in cardiac sarcolemmnal vesicles
(1990) Njue, Wilson N.; Liu, H.J.; Olley, P.N.
A [3H]azidophenacyl ester of PGE2 ([3H]azido-PGE2) was synthesized and used to photoaffinity label the protein component of the high affinity PGE2 binding site in cardiac sarcolemma membrane. Photolysis of the isolated cardiac sarcolemmal vesicles in the presence of [3H]azido-PGE2 resulted in the covalent labelling of a protein component that migrated on sodium dodecyl sulfate-polyacrylamide gels with an apparent molecular weight of 100,000. Incorporation of the [3H]azido-PGE2 did not occur in the absence of photolysis. The photolabelling of the 100-kDa protein by [3H]azido-PGE2 was inhibited by excess unlabelled PGE2 and azido-PGE2. Specific binding of [3H]azido-PGE2 was displaced by excess unlabelled PGE2 or azido-PGE2, but not PGF2 alpha, 6-keto-PGF1 alpha or PGD2. These results indicate that the 100-kDa photoaffinity labelled [3H]azido-PGE2 binding protein contains the binding site for PGE2 in isolated cardiac sarcolemma membranes.
The diagnostic value of haematuria and proteinuria in Schistosoma haematobium infection in Southern Nigeria.
(1992) Nwaorgu, O.C.; Anigbo, E.U.
Haematuria and proteinuria as detected by chemical reagent strips correlated moderately (r=0·7) with prevalence and intensity of infection with Schistosoma haematobium in an area of Anambra State, Nigeria. Differences attributable to age and sex were also reflected in a similar pattern, all peaks occurring in the 5–14 year age group. The differences observed with varying levels of intensity and haematuria at both 10 and 50 erythrocytes/μl (p<0·001) and proteinuria at 0·3 g/dl (p<0·01) were statistically significant. At a proteinuria level of 1 g/dl, the observed differences were however not statistically significant (p>0·5). The percentage of specimens from children (1–14 years) positive for S. haematobium eggs and with at least traces of haematuria and proteinuria (63·4% and 95%, respectively) was higher than in adults (33·3% and 80·2%, respectively). All individuals with more than 50 eggs/10 ml of urine were correctly identified using both indices either separately or in combination. For egg counts of less than 50 egg/10 ml of urine, false diagnosis occurred in only 5% of all specimens examined. The sensitivity and specificity of haematuria and proteinuria at trace quantities was very high, hut haematuria had a higher predictive value for a positive test (PvPt) and was considered the overall better indicator. A combination of both indices did not significantly increase the PvPt. When trace haematuria and moderate proteinuria were combined, both the sensitivity, specificity and PvPt were all above 90%, giving the best overall values in all the combinations made.
The influence of diel climatic cycle on the depth time distribution of phytoplankton and photosynthesis in a shallow equatorial lake (Lake Baringo), Kenya.
(Springer, 1995-05) Patterson, G.; Kotut, Kiplagat
Lake Baringo is a shallow equatorial lake. This paper reports a diel study of the depth-time distribution of phytoplankton and photosynthesis at one location in Lake Baringo on 10 March 1989. The water column shows a pattern of diurnal stratification probably accentuated by the high turbidity of the water and therefore rapid attenuation of solar energy. This stratified pattern breaks down at night due to atmospheric cooling and the regular onset of winds in the early evening. The phytoplankton is dominated by Microcystis aeruginosa with some associated epiphytes. It concentrates in the narrow euphotic zone during the diurnal period of stratification due to buoyancy of the Microcystis; evening breakdown of the thermocline results in the phytoplankton being mixed throughout the water column. A series of measurements of photosynthesis throughout the diurnal period gives an areal rate of 3.8 g O2 m−2 d−1. The relationship between this value and the level of fish exploitation in Lake Baringo is discussed. The diel cycle in Lake Baringo is interpreted as dominating over any seasonal limnological cycle in the lake.
Temporal changes in phytoplankton structure and composition at the Turkwel Gorge Reservoir, Kenya
(Kluwer Academic Publishers, 1998) Kotut, Kiplagat; Krienitz, L.; Muthuri, Francis M.
Temporal changes in phytoplankton chlorophyll a, composition, diversity, biomass (density and fresh weight) and primary production were investigated at the Turkwel Gorge Reservoir (Kenya) over a two year period (1994 and 1995). The phytoplankton properties investigated revealed a seasonal pattern that was very distinct in 1994 and muted in 1995. The wet season was characterized by higher levels of chlorophyll a, biomass and primary production and a lower diversity. A prominent seasonality in 1994 was found to be the result of a higher river inflow volume as compared to 1995. Chlorophyll a changes showed some positive correlation to changes in total nitrogen and total phosphorus. Diversity changes were inversely correlated to changes in total counts (R = −0.84 and −0.96 for 1994 and 1995 respectively). Individual species density changes varied from a distinct seasonal pattern to a nearly uniform density. While the diatom Achnanthes dominated the wet season in 1994, coccoid blue green algae were dominant during most of 1995. Throughout the study period, most biomass was due to the diatoms but with a lower percentage of total biomass in 1995 (40%) as compared to 1994 (88%). The wet season biomass in each year was dominated by the diatoms. Dominance of the intervening period changed irregularly between diatoms, dinoflagellates, green algae and blue green algae. The range of variation in chlorophyll a, total biomass and primary production were; 4.9 to 36.8 µg l-1, 440.14 to 11172.70 mg m-3 and 1.85 to 9.67 g O2 m-2 d-1 in 1994 and 4.9 to 11.5 µg l-1, 486.46 to 1351.39 mg l-1 and 3.08 to 5.41 g O2 m-2 d-1 in 1995 in the same order.
The Physico-chemical Conditions of Turkwel Gorge Reservoir, a New Man Made Lake in Northern Kenya
(1999) Kotut, Kiplagat; Njuguna, Stephen; Muthuri, Francis M.; Krienitz, L.
Variations in some physical, chemical, and nutrient conditions were investigated at Turkwel Gorge Reservoir and its inflowing river, Suam between 1994 and 1995. Seasonal changes in inflow volume had the greatest impact on the reservoir and river conditions investigated. A wide fluctuation in inflow volume combined with a regulated outflow independent of season resulted in a draw down of over 10 m in each year. Flood inflows during the wet season resulted in the lowest values of Secchi depth (range, 0.09-2.16 m), electrical conductivity (EC, range = 140-200 mS cm -1) and total alkalinity (TA, range = 75-111 mg 1-1) while the highest values were measured during the dry season. A functional relation between EC and TA (TA = 0.529 mg p1 EC: R ~ = 0.876) suggests a predominance of carbonates among the anions. Vertical profiles of temperature and dissolved oxygen (DO) revealed that the reservoir is monomictic with a wide variation in the depth of the daily mixed layer. High values of pH (range = 6.7-8.9) and DO (range = 4.9-9.2 mg V) were associated with periods of peak phytoplankton photosynthesis while the lowest values followed reservoir mixing. Peak total nitrogen (TN, range = 119-526 pg ki) and total phosphorus (TP, range = 8.9-71.6 pg 1-1) levels during the wet season resulted from increased river loading. Values of dissolved reactive silica (DRS, range = 0.41-9.77 mg kl) showed a wet season decline which was related to diatom depletion during the wet season. Annual reservoir areal loading rates of 27.38, 10.90 and 408.5 mg m -2 were computed for TN, TP and DRS respectively based on estimates of inflowing fiver loads in 1994. At the inflowing river Suam, low levels of EC (range =107-210 pS cm 1) and TA (range = 62-125 mg 1 -I) occurred during the wet season while the highest levels occurred shortly before the river dried up. The first flood water at the resumption of river inflow in March was characterized by very low levels of DO (range = 1.8-8.2 mg 11) and high levels of TN (range = 205-3354 pg 1 <) and TP (102-1259 pg 1-1). River pH (6.9-7.7) and DRS (range = 9.01-19.93 mg 1 -l) varied irregularly throughout the year.
Cyanotoxin-producing bloom of Anabaena flos-aquae, Anabaena discoidea and Microcystis aeruginosa (Cyanobacteria) in Nyanza Gulf of Lake Victoria, Kenya
(2002) Krienitz, L.; Ballot, A.; Wiegand, C.; Kotut, Kiplagat; Codd, G.A.; Pflugmacher, S.
A bloom of Anabaena flos-aquae, Anabaena discoidea and Microcystis aeruginosa, was characterized in Nyanza Gulf of Lake Victoria, near Kisumu, Kenya. According to classical literature data, A. discoidea was considered to be endemic to the Great Lakes of Africa. Its morphological characteristics are described and discussed in relation to A. flos-aquae. The two samples investigated contained the cyanobacterial toxins, microcystin-LR, -RR, -LA and -LF.
Bioactive steroidal alkaloid glycosides from Selanum aculeastrum.
(2002) Wanyonyi, Alphonse W.; Chhabra, S.C.; Mkoji, G.; Eilert, Udo; Njue, Wilson N.
Solanum aculeastrum Dunal was investigated for the presence of molluscicidal compounds. This led to the isolation of solaculine A, from the root bark in addition to known steroidal alkaloids; solamargine and beta-solamarine from the berries. The structures were elucidated by spectroscopic techniques. Molluscicidal activity of the aqueous extracts of the berries and root bark, and the isolated compounds were investigated.
Identification and distribution of pathogens coinfecting with Brucella spp., Coxiella burnetii and Rift Valley fever virus in humans, livestock and wildlife
(Wiley, 2002-01) Middlebrook, Earl A.; Romero, Alicia T.; Bett, Bernard; Nthiwa, Daniel M.; Oyola, Samuel O.; Fair, Jeanne M.; Bartlow, Andrew W.
Zoonotic diseases, such as brucellosis, Q fever and Rift Valley fever (RVF) caused by Brucella spp., Coxiella burnetii and RVF virus, respectively, can have devastating effects on human, livestock, and wildlife health and cause economic hardship due to morbidity and mortality in livestock. Coinfection with multiple pathogens can lead to more severe disease outcomes and altered transmission dynamics. These three pathogens can alter host immune responses likely leading to increased morbidity, mortality and pathogen transmission during coinfection. Developing countries, such as those commonly afflicted by outbreaks of brucellosis, Q fever and RVF, have high disease burden and thus common coinfections. A literature survey provided information on case reports and studies investigating coinfections involving the three focal diseases. Fifty five studies were collected demonstrating coinfections of Brucella spp., C. burnetii or RVFV with 50 different pathogens, of which 64% were zoonotic. While the literature search criteria involved ‘coinfection’, only 24/55 studies showed coinfections with direct pathogen detection methods (microbiology, PCR and antigen test), while the rest only reported detection of antibodies against multiple pathogens, which only indicate a history of co- exposure, not concurrent infection. These studies lack the ability to test whether coinfection leads to changes in morbidity, mortality or transmission dynamics. We describe considerations and methods for identifying ongoing coinfections to address this critical blind spot in disease risk management.
molluscicidal and antimicrobial activity of solanum aculeastrum
(2003) Wanyonyi, Alphonse W.; Chhabra, S.C.; Mkojo, G.; Njue, Wilson N.; Tarus, Paul K.
The methanolic extract of the fresh root bark and berries of Solanum aculeastrum showed significant activity against host snails of schistosomiasis. The berries extract was more potent with 100% snail kill at 50 ppm. Fractionation increased activity with 100% mortality at 20 ppm. The aqueous and methanolic extracts of the berries showed moderate antimicrobial activity, increasing by fractionation.
Contribution of tixic cynobacteria to massive deaths of lesser flamingoes at saline-alkaline lakes of Kenya
(2003) Krienitz, L.; Ballot, A.; Casper, P.; Codd, G.A.; Kotut, Kiplagat; Metcalf, J.S.; Morrison, L.F.; Pflugmacher, S.; Wiegand, C.
Heavy Metals and Pesticides in Marine Sediment, Seawater, and Seaplants Along the Kenya-Mombasa Coastline
(Taylor & Francis, 2003) Oyugi, Mildred P.; Chhabra, S.C.; Njue, Wilson N.; Kinyua, Anthony M.
Marine sediment, seawater and several species of seaplants along the Kenya- Mombasa coastal region were analyzed to determine the levels of heavy metals by AAS and EDXRF and organochlorine pesticides (OCPs) by GLC-ECD. In marine sediments, there were high levels of manganese (1100 mg/L) at Vanga, compared to other study sites. In seawater, the heavy metals were detected in levels higher than those considered as natural in the ocean and the range was 0.01–0.30 mg/L. OCPs were detected in marine sediments and in seaplants. The trend of concentration of these pollutants in ascending order in seawater, marine sediment and seaplants was observed.
In vitro antiplasmodial activity of some plants used in Kisii, Kenya against Malaria and their chloroquine potentiative effects.
(2003) Muregi, F.W.; Chhabra, S.C.; Njagi, Eliud N.; Lang’at-Thoruwa, C.; Njue, Wilson N.; Ndiege, I.O.
Fifty-five organic and aqueous extracts of 11 plants used in malaria therapy in Kisii District, Kenya were tested in vitro against chloroquine (CQ)-sensitive and resistant strains of Plasmodium falciparum. Of the plants tested, 73% were active (IC(50) < 100 microg/ml). Three plants, Vernonia lasiopus, Rhamnus prinoides and Ficus sur afforded extracts with IC(50) values ranging less than 30 microg/ml against both CQ-sensitive and resistant strains. Combination of some extracts with CQ against the multi-drug resistant P. falciparum isolate V1/S revealed some synergistic effect. The plant extracts with low IC(50) values may be used as sources for novel antimalarial compounds to be used alone or in combination with CQ.
Contribution of hot spring cyanobacteria to the mysterious deaths of Lesser Flamingos at Lake Bogoria, Kenya
(Elsevier, 2003-03-01) Krienitz, L.; Ballot, A.; Kotut, Kiplagat; Wiegand, C.; Pütz, S.; Metcalf, J.S.; Codd, G.A.; Pflugmacher, S.
Cyanobacterial mats at hot springs on the shore of the alkaline Lake Bogoria, Kenya, were investigated regarding species community and cyanobacterial toxin content. The hepatotoxins microcystin-LR, -RR, -LF and -YR, and the neurotoxin anatoxin-a were present. The mats were dominated by Phormidium terebriformis, Oscillatoria willei, Spirulina subsalsa and Synechococcus bigranulatus. The concentration of microcystins in mat samples, ranged from 221 to 845 microg microcystin-LR equivalents g(-1) DW of mat. Anatoxin-a concentrations ranged from 10 to 18 microg g(-1) DW of mat. A contribution of the cyanobacterial toxins from the hot spring mats to the mass mortalities of Lesser Flamingos is suggested by: (a), the presence of hot spring cyanobacterial cells and cell fragments, and high concentrations of the cyanobacterial hepato- and neurotoxins in flamingo stomach contents and faecal pellets; (b), observations of neurological signs of bird poisoning at the lake. Cyanobacterial toxins in stomach contents, intestine and fecal pellets were 0.196 microg g(-1) fresh weight (FW) for the microcystins and 4.34 microg g(-1) FW for anatoxin-a. Intoxication with cyanobacterial toxins could occur by uptake of detached cyanobacterial cells from the mats, as the flamingos need to drink fresh or brackish water, and to wash their feathers daily, which they do in the vicinity of the hot springs, where salinity is lower than in the main body of water of the lake.
A cyano-anomaly? Cyanobacterial toxins as contributors to Lesser Flamingo mass deaths
(2003-10) Codd, G.A.; Metcalf, J.S.; Morrison, L.F.; Krienitz, L.; Ballot, A.; Pflugmacher, S.; Wiegand, C.; Kotut, Kiplagat
In the present study, significative HAB’S bloom was confirmed in Matanchén Bay during Febrary 2003. The Raphidophice Fibrocapsa cf. japonica, Toriumi et Takano 1973 (=Chatonella japonica) has dominated (97%) red tide event occurring lately in coastal waters of Nayarit state, with high cell concentration of 4-6 millions of cells per liter of water. The duration of this bloom could not be determined exactly due to limiting sampling. There have been no reports of fish kills or human intoxication in the locality. This study represents the first survey on the distribution of Fibrocapsa cf. • Mexico japonica in the Mexican Pacific coast. The finding adds Raphidophyceans to the list of harmful algal blooms and toxin producers in Mexico.
Antiplamodial Activity of some Kenyan medicinal plant extracts singly and in combination with Chloroquine
(2004) Muregi, F.W.; Chabbra, S.C.; Njue, Wilson N.; Njagi, Eliud N.; Langa’t, C.; Ndiege, I.O.
Sixty organic and aqueous extracts of eleven plants used for the control of malaria by local communities in Kisii District, Kenya were screened for in vitro anti-plasmodial activity. The plants selection was based on existing ethnobotanical information and interviews with local communities. The extracts were tested against chloroquine sensitive and resistant laboratory adapted strains of Plasmodium falciparum. The study revealed that 63.6% of the plants were active (IC50 < or = 100 microg/mL). Extracts of four plants, Ekebergia capensis, Stephania abyssinica, Ajuga remota and Clerodendrum myricoides gave IC50 values below 30 microg/mL against both chloroquine sensitive and resistant P. falciparum strains. Combination of extracts of E. capensis and C. myricoides with chloroquine against the multi-drug resistant P. falciparum isolate (V1/S) revealed synergistic effect. The plants which showed activity may be useful as sources for novel anti-plasmodial compounds.
Anti-plasmodial Activity of Some Kenyan Medicinal Plant Extracts Singly and in Combination with Chloroquine
(Wiley InterScience, 2004) Muregi, F.W.; Chhabra, S.C.; Njagi, Eliud N.; Lang’at, C.; Njue, Wilson N.; Orago, A.S.; Omar, S.A.; Ndiege, I.O.
Sixty organic and aqueous extracts of eleven plants used for the control of malaria by local communities in Kisii District, Kenya were screened for in vitro anti-plasmodial activity. The plants selection was based on existing ethnobotanical information and interviews with local communities. The extracts were tested against chloroquine sensitive and resistant laboratory adapted strains of Plasmodium falciparum. The study revealed that 63.6% of the plants were active (IC50 ≤ 100 μg/mL). Extracts of four plants, Ekebergia capensis, Stephania abyssinica, Ajuga remota and Clerodendrum myricoides gave IC50 values below 30 μg/mL against both chloroquine sensitive and resistant P. falciparum strains. Combination of extracts of E. capensis and C. myricoides with chloroquine against the multi-drug resistant P. falciparum isolate (V1/S) revealed synergistic effect. The plants which showed activity may be useful as sources for novel anti-plasmodial compounds.
Cyanobacteria and cyanobacterial toxins in the alkaline crater lakes Sonachi and Simbi, Kenya
(Elsevier, 2005-01) Ballot, A.; Krienitz, L.; Kotut, Kiplagat; Wiegand, C.; Pflugmacher, S.
The phytoplankton communities and the production of cyanobacterial toxins were investigated in two alkaline Kenyan crater lakes, Lake Sonachi and Lake Simbi. Lake Sonachi was mainly dominated by the cyanobacterium Arthrospira fusiformis, Lake Simbi by A. fusiformis and Anabaenopsis abijatae. The phytoplankton biomasses measured were high, reaching up to 3159 mg l−1 in L. Sonachi and up to 348 mg l−1 in L. Simbi. Using HPLC techniques, one structural variant of the hepatotoxin microcystin (microcystin-RR) was found in L. Sonachi and four variants (microcystin-LR, -RR, -LA and -YR) were identified in L. Simbi. The neurotoxin anatoxin-a was found in both lakes. To our knowledge this is the first evidence of cyanobacterial toxins in L. Sonachi and L. Simbi. Total microcystin concentrations varied from 1.6 to 12.0 μg microcystin-LR equivalents g−1 DW in L. Sonachi and from 19.7 to 39.0 μg microcystin-LR equivalents g−1 DW in L. Simbi. Anatoxin-a concentrations ranged from 0.5 to 2.0 μg g−1 DW in L. Sonachi and from 0 to 1.4 μg g−1 DW in L. Simbi. In a monocyanobacterial strain of A. fusiformis, isolated from L. Sonachi, microcystin-YR and anatoxin-a were produced. The concentrations found were 2.2 μg microcystin g−1 DW and 0.3 μg anatoxin-a g−1 DW. This is the first study showing A. fusiformis as producer of microcystins and anatoxin-a. Since A. fusiformis occurs in mass developments in both lakes, a health risk for wildlife can be expected.
Metal status of Nairobi riverwaters and their bioaccumulation in Labeo cylindricus
(Academic Journals, 2005-03) Budambula, Nancy; Mwachiro, E.C.
This study focused on the analysis of metals in water and fish from Nairobi River. Water from Kikuyu, Kawangware, Chiromo, Eastleigh, Njiru and Fourteen Falls along the Nairobi River was analyzed for the presence of metals. Most of the metal levels in water were below the critical limit of World Health Organization and Kenya Bureau of Standards except for lead, chromium, iron and manganese. Isolated cases of mercury and aluminium pollution were recorded. Except for iron, sodium and potassium, there was no significant difference in the concentration of metals at different sites. This study also analyzed metal levels in fish organs and tissues of fish caught from downstream (Fourteen Falls). The highest zinc concentration (360 μg/g) was in the scales, copper recorded the highest concentration in the kidney (45 μg/g), while cadmium recorded high values (167 μg/g) in the heart. Lead recorded high values (178 μg/g) in the heart and mercury recorded high values also in the heart (1000 ng/g). Most of these organs, are however, not eaten by man as food. Although metal levels were within normal levels in the water at Fourteen Falls, mercury, copper, lead and iron recorded higher than accepted levels in some fish organs. This calls for caution in the consumption of fish from Fourteen Falls.

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