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Biomedical subjects

M Rowland

Publications and source records attributed to M Rowland.

300 records · Page 17Linked to original sources
PubMedDate not supplied

Transmission and control of vivax malaria in Afghan refugee settlements in Pakistan.

Regular biting collections were conducted in 1993-1994 to investigate seasonal fluctuations in the abundance of anophelines in Afghan refugee villages in north-western Pakistan. Enzyme-linked immunosorbent assay were used to test heads-plus-thoraces for the presence of malaria sporozoites. Anophelines giving positive results for Plasmodium vivax were captured in every month except January. Nine species were positive. Biting rates showed a marked increase in May, after the spring rains, and thus spring transmission of vivax malaria seems certain. However, transmission of vivax malaria reached its peak only after the monsoon in July. To determine the optimal time to control vivax malaria by indoor spraying with residual insecticide, spray campaigns were conducted in either spring or summer in 14 refugee villages. Villages sprayed in July 1994 showed a mean reduction in annual incidence of 62% (95% confidence interval [CI] +/-6%) relative to the previous year, whereas villages sprayed in April 1994 showed only a 15% reduction (95% CI +/- 32%). Parasite prevalence surveys conducted in April and October 1994 confirmed the greater efficacy of spray campaigns waged in July. The insecticide malathion proved as effective as the pyrethroid lambdacyhalothrin, even though several species of anopheline were resistant to malathion.

Afghanistan↗
PubMedDate not supplied

Anthroponotic cutaneous leishmaniasis in Kabul, Afghanistan: vertical distribution of cases in apartment blocks.

Owing to the civil war, the inhabitants of Kabul in Afghanistan are suffering a major epidemic of anthroponotic cutaneous leishmaniasis (ACL) caused by Leishmania tropica. Surveys conducted among children in 2 high-rise apartment blocks in the city revealed that the prevalence of active lesions was much lower on upper stories: 84% lower in one block (chi 2 = 7.13, d.f. = 1, P = 0.008) and 54% lower in the other (chi 2 = 6.17, d.f. = 1, P = 0.01). Similar trends were apparent with regard to scars from old lesions. These results suggest that in Kabul most transmission of ACL takes place in the home. In addition, the results imply that there must be limited vertical movement of the vector within apartment blocks. Together, these findings suggest that indoor spraying should be an effective means of control and that insecticidal applications could probably be restricted to lower stories.

Adolescent↗
PubMedDate not supplied

Randomized controlled trials of 5- and 14-days primaquine therapy against relapses of vivax malaria in an Afghan refugee settlement in Pakistan.

Primaquine is the only drug available that can eliminate hypnozoites from the liver and prevent relapses of vivax malaria. The World Health Organization recommends a course of 14-21 days depending on region and strain. The National Malaria Control and Eradication Programmes of Pakistan and India have adhered to a 5-day course as their standard as it is deemed more practical to implement and because facility for detecting glucose 6-phosphate dehydrogenase (G6PD) deficiency is seldom available at the periphery. Evidence for the efficacy of the 5-day regimen is controversial or lacking. Two, year-long, randomized controlled trials were undertaken in an Afghan refugee camp in north-western Pakistan using a process of passive case detection and treatment at the camp's clinic: the first trial compared treatment with chloroquine alone versus chloroquine plus 5-days primaquine, the second trial compared chloroquine alone versus chloroquine plus 14-days primaquine. Chloroquine is not hypnozoitocidal and was administered to eliminate the erythrocytic stages and to alleviate clinical symptoms. The daily primaquine dose was 0.25 mg/kg bodyweight and the total chloroquine dose was 25 mg/kg over 3 days. During the first trial 52% (129/250) of the non-primaquine group recorded a 2nd clinical-parasitaemic episode and 23% recorded a 3rd, whereas 51% (128/250) of the 5-days primaquine group reported a 2nd episode and 21% recorded a 3rd. During the second trial 49% (49/100) of the non-primaquine group recorded a 2nd episode and 25% recorded a 3rd, whereas only 32% (32/100) of the 14-days primaquine group recorded a 2nd and only 2% recorded a 3rd. The 5-days primaquine regimen has no value as an anti-relapse therapy and should be abandoned. In extended tests in vivo in which vivax cases (n = 31) were treated with chloroquine 25 mg/kg and 14-days primaquine, there was no parasite recrudescence within 28 days and hence no evidence of resistance to chloroquine.

Adolescent↗
PubMedDate not supplied

An outbreak of cutaneous leishmaniasis in an Afghan refugee settlement in north-west Pakistan.

Cutaneous leishmaniasis (CL) due to Leishmania tropica appears to be an emerging disease in parts of north-east Afghanistan and north-west Pakistan. Timargara, an Afghan refugee camp of 17 years' standing, in the district of Dir, North West Frontier Province of Pakistan, experienced a major outbreak of CL in 1997 for the first time. As part of the investigation, each section of the camp was surveyed for CL. Around 38% of the 9200 inhabitants bore active lesions and a further 13% had scars from earlier attacks. According to interview statements, 99% of earlier infections had healed within the previous 2 years. To confirm the diagnosis, a sample of current CL lesions was examined parasitologically. Amastigotes were detectable by microscopy in only 36% of lesions. However, 48% of slide-negative cases produced positive cultures and some cases negative to both microscopy and culture were positive by PCR. Overall detection rate was about 80%. The sandfly Phlebotomus sergenti, a known vector of L. tropica, was captured within the camp, indicating local transmission. CL has not been reported from this area of Pakistan before. Although the majority of refugees left Afghanistan 2 decades ago, cross-border movement of men is common. The Afghanistan capital, Kabul, is currently experiencing a major epidemic of CL; infected migrant carriers from Kabul are probably the source of the outbreak in Timargara.

Adolescent↗
PubMedDate not supplied

Permethrin-treated chaddars and top-sheets: appropriate technology for protection against malaria in Afghanistan and other complex emergencies.

Insecticide-treated mosquito nets (ITN) provide excellent protection against malaria; however, they have a number of shortcomings that are particularly evident in politically unstable countries or countries at war: not everyone at risk can necessarily afford a net, nets may be difficult to obtain or import, nets may not be suitable for migrants or refugees sleeping under tents or plastic shelter. There is a need to develop cheaper, locally appropriate alternatives for the most impoverished and for victims of complex emergencies. Afghan women, in common with many Muslim peoples of Asia, wear a veil or wrap known as a chaddar to cover the head and upper body. This cloth doubles as a sheet at night, when they are used by both sexes. A randomized controlled trial was undertaken in which 10% of the families of an Afghan refugee camp (population 3950) in north-western Pakistan had their chaddars and top-sheets treated with permethrin insecticide at a dosage of 1 g/m2 while a further 10% had their chaddars treated with placebo formulation. Malaria episodes were recorded by passive case detection at the camp's health centre. From August to November the odds of having a falciparum or vivax malaria episode were reduced by 64% in children aged 0-10 years and by 38% in refugees aged < 20 years in the group using permethrin-treated chaddars and top-sheets. Incidence in refugees over 20 years of age was not significantly reduced. The cost of the permethrin treatment per person protected (US$0.17) was similar to that for treating bednets (and cost only 10-20% of the price of a new bednet). An entomological study simulating real-life conditions indicated that host-seeking mosquitoes were up to 70% less successful at feeding on men sleeping under treated chaddars and some were killed by the insecticide. Permethrin-treated top-sheets and blankets should provide appropriate and effective protection from malaria in complex emergencies. In Islamic and non-Islamic countries in Asia, treated chaddars and top-sheets should offer a satisfactory solution for the most vulnerable who cannot afford treated nets.

Adolescent↗
PubMedDate not supplied

Use of a single-pass in situ perfused rat hindlimb to study tissue distribution kinetics. Method development and experiences with Evans blue.

A single-pass in situ rat hindlimb preparation has been developed as an alternative to the isolated perfused preparation to study tissue drug distribution kinetics with minimal disturbance of the animal physiology. Evans blue (EB), a vascular marker, was administered (in saline or plasma) as a bolus into the femoral artery, and the total outflow blood was collected at timed intervals from the corresponding femoral vein. Donor blood was infused through the jugular vein at a rate that matched the loss. No changes in the blood flow or development of edema were observed. The outflow profile was characterized using statistical moments. Regardless of the injected solution, the estimated vascular volume (10% of the hindlimb wet weight) was higher than that reported for the isolated rat hindlimb (4.1%) but closer to the in vivo blood volume (6.8-8.1% of body weight for 250-g rat) and sum of vascular volumes of its composite tissues (6.9% of tissue weights). The large normalized variance (CV(2)) of the outflow (2.2+/-0.1) confirms the known heterogeneity of the hindlimb. Entrapment in the limb (approximately 4%) and escape to the rest of the body could explain the incomplete recovery (79-89%) of the dye.

Algorithms↗
PubMedDate not supplied

Laboratory evaluation of pyriproxifen treated bednets on mosquito fertility and fecundity. A preliminary study.

AIM: The study evaluated the effect of pyriproxifen treated bednets on mosquito fertility and fecundity in the laboratory. Pyriproxyfen (insect growth regulator) has been considered as a possible tool for management of pyrethroid resistance in mosquitoes. There are documentations of the effectiveness of pyriproxifen in controlling larval development when applied directly to breeding site. Considerations have been given to the use of pyriproxyfen on bed nets for sterilizing effect on mosquitoes resistant to pyrethroids. METHOD: Groups of mosquitoes (Anopheles stephensi Beech) were exposed to bednet treated with 2% Pyriproxyfen and untreated netting 24 hrs after blood feeding. After oviposition, egg counts were done for each mosquito in the two groups. Larvae emerging from the laid eggs by each mosquito were counted. Three sets of experiments were successful. RESULTS: There was no significant difference in number of eggs laid between the two treatment groups (p=0.177). There was statistically significant difference in the number of laid eggs that hatched between the treatment types (p=0.0061). There was also statistically significant difference in the mean number of eggs that hatched between the experiments (p=0.0013). The mean number of eggs retained in the pyriproxyfen group was higher (70.3) than in the control group (41.6). This difference was not statistically significant with the small sample tested (p=0.08). CONCLUSION: The results suggest that 2% pyriproxyfen on bed nets has no effect on An. stephensi fecundity. Reduced fertility of eggs laid by mosquitoes exposed to pyriproxyfen treated bed nets was observed.

Animals↗
PubMedDate not supplied

Pharmacokinetics of prednisone and prednisolone at steady state in the rabbit.

A range (approximately 0.2-2.0 micrograms/min/kg) of constant rate iv infusions of prednisolone (as the phosphate ester) was administered to five rabbits either singly or as two consecutive infusions, and then again at about the same rates of infusion as part of multiple infusion studies. Prednisone (as the succinate) was also infused at three different infusion rates (range, 1.5-15 micrograms/min/kg) to four of the five rabbits. Plasma concentrations of prednisolone and prednisone at steady state were measured by HPLC. The binding of prednisone and prednisolone in plasma was measured by equilibrium dialysis. The multiple infusion studies demonstrated that the nonlinearity in plasma clearance of prednisolone could not be attributed to any time-dependent effect. The average plasma clearance of prednisolone increased by 250% when its rate of infusion was increased 10-fold. The ranges of clearance values at low and high rates of infusion were 2.51-4.08 and 6.08-10.98 ml/min/kg, respectively. The binding of prednisolone in plasma was found to be concentration dependent. At the lower rates of infusions, the clearance of unbound prednisolone appeared to increase on increasing its rate of infusion but remained relatively constant thereafter (greater than 1.0 microgram/min/kg). The ranges of unbound plasma prednisolone clearance at low and high rates of infusions were 30.3-67.7 and 50.6-110.2 ml/min/kg, respectively. The percentage of unbound prednisone increased on increasing the total plasma prednisone concentration (ranges at low and high concentrations of prednisone were 15.5-33.7 and 32.3-47.6%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Relationship between lipophilicity and hepatic dispersion and distribution for a homologous series of barbiturates in the isolated perfused in situ rat liver.

The hepatic disposition kinetics of a homologous series of 5-n-alkyl-5-ethyl barbituric acids (methyl, ethyl, propyl, butyl, and pentyl) were determined using a single-pass perfused in situ rat liver preparation. The perfusion experiments were conducted using protein-free Krebs bicarbonate medium, delivered at a constant flow of 15 ml/min. Each barbiturate was injected separately into the portal vein as a rapid bolus (25 micrograms/50 microliters) at appropriate intervals in a random order. The venous outflow concentrations of the barbiturates were determined by HPLC. A nonlinear least squares program was used to fit the axial dispersion model of hepatic elimination to the outflow profiles. With increasing length of the alkyl chain, there was a significant increase in the volume of distribution in the liver (0.85 +/- 0.12 ml/g for methyl and 4.87 +/- 1.27 ml/g for pentyl), which led to an increased organ mean transit time (35 +/- 2.4 sec for methyl and 223 +/- 32.8 sec for pentyl). The increased volume of distribution may have arisen from greater binding to intracellular proteins and/or greater partitioning into lipophilic components of hepatic tissue. The dispersion numbers of this homologous series, a measurement of relative axial spreading, were similar (0.28-0.39), despite the wide range of log P values (0.02-2.23) among them. The similarity between the dispersion number for each barbiturate and that for reference markers (erythrocytes, albumin, and water) suggests that the relative axial spreading of these barbiturates is determined primarily by the heterogeneity of the hepatic vasculatory system.

Animals↗