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D K Koech

Publications and source records attributed to D K Koech.

At least 73 records · Page 4Linked to original sources
PubMed1987

Dependence of hatching of Schistosoma haematobium miracidia on physical and biological factors.

The effects of light, agitation, and salinity on the hatching pattern of Schistosoma haematobium eggs were examined. Whereas all three factors influenced the hatching pattern, only salinity affected the hatching rate. Eggs began to hatch 5 min after dilution and reached a peak 10-15 min after dilution when urination, dilution of urine, and observation of hatching were conducted under ordinary laboratory conditions (25 degrees C in diffuse sunlight). Complete darkness delayed hatching. Agitation of urine by aspiration into a syringe accelerated egg hatching, the miracidia reaching peak numbers 5 min earlier.

Animals↗
PubMed1987

Community-based malaria control in Saradidi, Kenya: description of the programme and impact on parasitaemia rates and antimalarial antibodies.

A community-based malaria control programme initiated in Saradidi, Kenya in 1982 is described. Antimalarial treatment provided by volunteer community health workers was made available in each village. Malaria was holoendemic. Parasitaemia rates by age were high and did not change after the control programme began. Plasmodium falciparum was the most common species and was present alone or mixed in 98.2% of 8105 infections. Virtually all (98.5%) of 2040 blood samples collected in May 1981 were positive (reciprocal titre greater than or equal to 80) to P. falciparum by the indirect fluorescent antibody (IFA) test. Seropositivity rates to P. falciparum in the IFA test or the enzyme-linked immunosorbent assay (ELISA) were high in all age groups and did not change significantly in longitudinal surveys or in a cohort of children zero to nine years old followed at intervals. While the malaria control programme was successful in bringing treatment to each village, malaria prevalence was not reduced. Parasitologic and serologic studies alone were not adequate to describe the impact of the community-based malaria control programme in Saradidi. Morbidity and mortality rates caused by malaria can decline, significantly improving the health of the population, in the absence of any decrease in parasitaemia rates.

Animals↗
PubMed1987

Changing response to chloroquine of Plasmodium falciparum in Saradidi, Kenya, from 1981 to 1984.

From 1981 through 1984, the response of Plasmodium falciparum to chloroquine was monitored in Saradidi, Kenya, as a part of a community-based health programme to provide treatment for malaria in each village. Before 1983, all 71 infections treated with chloroquine were sensitive in vivo; parasitaemia cleared by day 3 and remained absent to day 7. In June 1983, 23.1% of 26 infections treated with chloroquine base 10 mg kg-1 either recrudesced in seven days (RI resistance, five infections) or decreased but failed to clear (RII resistance, one infection). In September 1983, 16.2% of 68 and in February 1984, 13.2% of 53 infections were resistant in vivo after treatment with chloroquine base 10 mg kg-1. A course of chloroquine base 25 mg kg-1 over three days remained effective; only two (1.6%) of 129 infections examined were resistant in vivo; in both, parasitaemia cleared then recurred (RI). In September 1984, however, nine (10.2%) infections were resistant after treatment with chloroquine base 25 mg kg-1; in four of these parasitaemia decreased but never cleared (RII). Similar results were observed in vitro. In the Rieckmann macro in vitro test, 63.3% of 30 P. falciparum isolates tested were resistant to chloroquine (minimal inhibitory concentration (MIC) greater than or equal to 1.25 X 10(-6) mol 1(-1) blood) in June 1983, as were 61.8% of 34 isolates in the Rieckmann micro test (MIC greater than or equal to 1.14 X 10(-6) mol 1(-1) blood).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Subpopulations of T lymphocytes in Kenyan patients with visceral leishmaniasis.

Populations of peripheral blood T lymphocytes from patients with Kenyan visceral leishmaniasis were studied using specifically defined antisera (monoclonal antibodies, Ortho-mune OKT3, OKT4, OKT6, and OKT8). The levels of total T lymphocytes and circulating thymocytes were within the same range as those of clinically normal individuals. However, the proportions of the helper/inducer T cells were lower in untreated patients than in the controls (18.9% vs. 39.7%) while the levels of suppressor/cytotoxic T cells were higher than in the controls (40.5% vs. 27.8%). After successful antileishmania treatment these levels showed a gradual return towards normal over a period of one year. It was concluded that immunosuppression observed is due to the levels of peripheral blood helper/inducer and suppressor/cytotoxic T lymphocytes.

Adolescent↗
PubMed1987

Contribution of adherent cells and serum components to immune suppression in Kenyan visceral leishmaniasis.

Adherent cells and serum components from Kenyan patients with visceral leishmaniasis were examined with the view to evaluating their contribution to cell-mediated immune suppression. Mitogens (phytohemagglutinin and concanavalin A) and antigens (purified protein derivative, streptokinase-streptodornase, and leishmania) were used as stimulants. Compared to the controls, the contribution of serum components to suppression in presence of any of the mitogens and antigens was not significant. The same applied to adherent cells, except in the presence of leishmania antigen where adherent cells contributed significantly (P less than 0.001). Removal of adherent cells from peripheral blood mononuclear cells of patients and controls considerably increased in vitro lymphocyte responses to both mitogens and antigens (by about twice), suggesting that in this study, the inhibition of in vitro lymphocyte responses to antigens and mitogens by adherent cells was a general phenomenon independent of the presence of the disease.

Humans↗
PubMed1987

In vitro susceptibility of Plasmodium falciparum isolates from Jilore, Kenya, to antimalarial drugs.

Twenty-six Plasmodium falciparum isolates obtained during a prophylaxis study at Jilore primary school, Malindi, Kenya, were adapted to in vitro culture and their susceptibility to 13 antimalarial drugs was tested by a modified radioisotopic method. Pyrimethamine, chloroquine, amodiaquine, cycloguanil, chlorcycloguanil, quinine, quinidine and sulfadoxine, and the experimental compounds MB 35769, mefloquine, WR 184806, parvoquone, and menoctone were used. The isolates could be divided into two groups with significantly different susceptibility to pyrimethamine, shown by a 755-fold difference in the mean ID50 values (2.77 +/- 1.98 x 10(-10) mol/l and 2.09 +/- 1.64 x 10(-7) mol/l). The mean susceptibility of the two groups differed 7.7-fold for chlorcycloguanil and 14.6-fold for cycloguanil, but were not significantly different for the other drugs. All isolates were more sensitive to amodiaquine than to chloroquine in vitro. The ratio of the geometric mean ID50 values of chloroquine to amodiaquine was 3.13. The ratio for the chemically related compounds parvoquone to menoctone was 5.63, quinine to quinidine was 5.58, and mefloquine to WR 184806 was 12.16.

Animals↗
PubMed1986

Response of Plasmodium falciparum to dihydrofolate reductase inhibitors in Malindi, Kenya.

The response of Plasmodium falciparum isolates to dihydrofolate reductase inhibitors (DHFRI) was examined in Malindi, Kenya. All 20 infected children treated with pyrimethamine/sulphadoxine responded. In contrast, after treatment with pyrimethamine, parasitaemia in 9 of 14 infections failed to clear or recrudesced during the seven-day follow-up. In a 48-hour in vitro test, five of six isolates resistant to pyrimethamine in vivo had a minimal inhibitory concentration (MIC) to pyrimethamine greater than or equal to 300 nmoles/1 compared with less than or equal to 100 nmoles/1 for the four sensitive isolates; four isolates did not grow. MIC to M-B 35769, an experimental DHFRI structurally similar to pyrimethamine were the same (six isolates) or 10-fold lower (three isolates). In the laboratory four of five isolates adapted to in vitro culture had the same MICs as in the field while one isolate became less responsive to both drugs. Cycloguanil (the active metabolite of proguanil) was more active in vitro in the laboratory than pyrimethamine or M-B 35769.

Child↗
PubMed1984

Effectiveness of amodiaquine as treatment for chloroquine-resistant Plasmodium falciparum infections in Kenya.

Studies were conducted in Malindi, Kenya, to assess the response of Plasmodium falciparum to chloroquine and amodiaquine in vivo (by an extended 14-day test) and in vitro (with the Rieckmann micro test). In-vivo resistance was demonstrated in 19 of 69 (28%) infections treated with chloroquine, but in only 2 of 60 (3.3%) of those treated with amodiaquine (p less than 0.001). In-vitro resistance to chloroquine was demonstrated in 15 of 23 (65%) tests. In contrast, 22 of the same 23 isolates were sensitive to amodiaquine in vitro. Effective concentrations by probit analysis for 50% and 99% (EC50 and EC99) inhibition, respectively, were 180.7 and 4319.6 nmol/l for chloroquine and 12.2 and 147.0 nmol/l for amodiaquine. The results suggest that amodiaquine is effective for the treatment of chloroquine-resistant falciparum malaria in Kenya.

Adolescent↗
PubMed1984

Precipitates found around Schistosoma haematobium eggs from human urine prior to circumoval precipitin test.

Schistosoma haematobium eggs were recovered in urine from schoolchildren in Mwachinga Village, Kwale District, Kenya. The surface of the eggs showed a pattern similar to that observed in a circumoval precipitin (COP) test. Observed precipitates were removed by treatment of the eggs with pepsin, but were not affected by trypsin. Similar precipitates occurred after incubating the pepsin-treated eggs with urine supernatants from the same children. Attempts were made to identify the components that might contribute to observed bleb (precipitate) formation. The fluorescent antibody test revealed both IgG and IgM in the precipitate, while urine examination by immunodiffusion revealed IgG, IgM, IgA and C3. These components probably participated in the bleb formation. This possibility seemed more likely because of the presence of anti-egg antibodies in the immunoglobulins identified in the urine, and agrees well with the expected activity of pepsin on these immunoglobulins. These results, therefore, suggest that S. haematobium eggs recovered in urine contain precipitates formed mainly by immunoglobulins; it is necessary to treat such eggs with pepsin before carrying out a COP test. The relevance of these findings to the immunodiagnosis of Schistosomiasis haematobium in man is discussed.

Adolescent↗
PubMed1984

A new in vitro test for pyrimethamine/sulfadoxine susceptibility of Plasmodium falciparum and its correlation with in vivo resistance in Kenya.

A useful in vitro method for field evaluation of Plasmodium falciparum sensitivity to pyrimethamine/sulfadoxine is described. Thirty-five Kenyan schoolchildren infected with P. falciparum were treated with this drug combination and followed up for 5 weeks. In vitro tests for sensitivity to these drugs and to chloroquine were performed before starting treatment. All infections cleared within 7 days of treatment, but 5 children had recurrent parasitaemia within 35 days. The original isolates from 4 of these 5 children had an in vitro response to pyrimethamine/sulfadoxine similar to a known strain that was resistant to these drugs; only 4 of the remaining 30 isolates from patients in whom recurrent parasitaemia did not occur had a resistant in vitro response (P = 0.006). In the patient with recurrent parasitaemia whose initial isolate appeared sensitive to pyrimethamine/sulfadoxine, the recurrent isolate had a resistant pattern in vitro, suggesting either reinfection or selection of a resistant subpopulation following treatment. The in vitro response to this drug combination was correlated with the in vitro response to either drug alone and with the in vitro response to chloroquine. Two of the 5 infections with recurrent parasitaemia after initial pyrimethamine/sulfadoxine treatment were resistant to chloroquine in vivo. The in vitro test for pyrimethamine/sulfadoxine should be useful for mapping the spread of multidrug-resistant P. falciparum.

Adolescent↗