Biology & control of Anopheles culicifacies Giles 1901

Malaria epidemiology is complex due to multiplicity of disease vectors, sibling species complex and variations in bionomical characteristics, vast varied terrain, various ecological determinants. There are six major mosquito vector taxa in India, viz. Anopheles culicifacies, An. fluviatilis, An. stephensi, An. minimus, An. dirus and An. sundaicus. Among these, An. culicifacies is widely distributed and considered the most important vector throughout the plains and forests of India for generating bulk of malaria cases (>60% annually). Major malaria epidemics are caused by An. culicifaices. It is also the vector of tribal malaria except parts of Odisha and Northeastern States of India. An. culicifacies has been the cause of perennial malaria transmission in forests, and over the years penetrated the deforested areas of Northeast. An. culicifacies participates in malaria transmission either alone or along with An. stephensi or An. fluviatilis. The National Vector Borne Disease Control Programme (NVBDCP) spends about 80 per cent malaria control budget annually in the control of An. culicifacies, yet it remains one of the most formidable challenges in India. With recent advances in molecular biology there has been a significant added knowledge in understanding the biology, ecology, genetics and response to interventions, requiring stratification for cost-effective and sustainable malaria control. Research leading to newer interventions that are evidence-based, community oriented and sustainable would be useful in tackling the emerging challenges in malaria control. Current priority areas of research should include in-depth vector biology and control in problem pockets, preparation of malaria-risk maps for focused and selective interventions, monitoring insecticide resistance, cross-border initiative and data sharing, and coordinated control efforts for achieving transmission reduction, and control of drug-resistant malaria. The present review on An. culicifacies provides updated information on vector biology and control outlining thrust areas of research.

Dengue, an emerging arboviral infection in Assam, northeast India

Dengue is emerging as major public health concern in northeast India and spreading with increased morbidity. Most cases were recorded in Guwahati metropolitan city of the state of Assam during post-monsoon months (September- December). These comprised all age groups of both sexes with significantly higher incidence of cases in adult males aged 26- 60 years.

Status of DDT and pyrethroid resistance in Indian Aedes albopictus and absence of knockdown resistance (kdr) mutation

BACKGROUND & OBJECTIVES

Aedes albopictus is one of the vectors for dengue and chikungunya and emergence of pyrethroid resistance in this species could be of a major concern in controlling the vector. This study reports insecticide susceptibility status of Ae. albopictus to DDT and pyrethroids in some Indian populations and status of presence of knockdown resistance (kdr) mutations.

METHODS

Three to four day old adult female Ae. albopictus collected from Delhi, Gurgaon (Haryana), Hardwar (Uttarakhand), Guwahati (Assam) and Kottayam (Kerala) were bio-assayed with DDT (4%), permethrin (0.75%) and deltamethrin (0.05%) impregnated papers using WHO standard susceptibility test kit. Mosquitoes were PCRgenotyped for F1534C kdr-mutation in the voltage-gated sodium channel (VGSC) gene. DDT and pyrethroid resistant individuals were sequenced for partial domain II, III and IV of VGSC targeting residues S989, I1011, V1016, F1534 and D1794 where kdr mutations are reported in Ae. aegypti.

RESULTS

Adult bioassays revealed varying degree of resistance against DDT among five populations of Ae. albopictus with corrected mortalities ranging between 61 and 92%. Kerala and Delhi populations showed incipient resistance against permethrin and deltamethrin respectively. All other populations were susceptible for both the synthetic pyrethroids. None of the kdr mutations was detected in any of DDT, deltamethrin and permethrin resistant individuals.

INTERPRETATION & CONCLUSION

Ae. albopictus has developed resistance against DDT and there is emergence of incipient resistance against pyrethroids in some populations. So far, there is no evidence of presence of knockdown resistance (kdr) mutation in Ae. albopictus.

Mosquito-borne diseases in Assam, north-east India: current status and key challenges

Mosquito-borne diseases, including malaria, Japanese encephalitis (JE), lymphatic filariasis and dengue, are major public health concerns in the north-eastern state of Assam, deterring equitable socioeconomic and industrial development. Among these, malaria and JE are the predominant infections and are spread across the state. The incidence of malaria is, however, gradually receding, with a consistent decline in cases over the past few years, although entry and spread of artemisinin-resistant Plasmodium falciparum remains a real threat in the country. JE, formerly endemic in upper Assam, is currently spreading fast across the state, with confirmed cases and a high case-fatality rate affecting all ages. Lymphatic filariasisis is prevalent but its distribution is confined to a few districts and disease transmission is steadily declining. Dengue has recently invaded the state, with a large concentration of cases in Guwahati city that are spreading to suburban areas. Control of these diseases requires robust disease surveillance and integrated vector management on a sustained basis, ensuring universal coverage of evidence-based key interventions based on sound epidemiological data. This paper aims to present a comprehensive review of the status of vector-borne diseases in Assam and to address the key challenges.

Dengue vectors in urban and suburban Assam, India: entomological observations

BACKGROUND

Dengue is rapidly becoming established in north-east India and spreading, on account of rapid urbanization and population movement, with reported morbidity and attributable death cases. This study aims to determine the seasonal abundance of Aedes (Stegomyia) albopictus and Aedes (Stegomyia) aegypti in Guwahati metropolis and suburban settlements; to characterize the breeding resources for these mosquitoes; and to ascertain the status of their susceptibility to adulticides and larvicides.

METHODS

Mosquito larval surveys were carried out in different localities in both Guwahati city and adjoining suburbs from January to December 2013, to determine the seasonal abundance of disease vectors and their breeding preferences. The insecticide susceptibility status of mosquito adults and larval populations of both Aedes aegypti and Aedes albopictus was ascertained, using World Health Organization standard diagnostic concentrations and test procedures.

RESULTS

The study revealed that both Aedes aegypti and Aedes albopictus are widely abundant in Guwahati city and suburbs, and breeding in a wide variety of resources. Aedes albopictus, however, was the predominant mosquito species in suburbs, breeding preferentially in flower vases, cut-bamboo stumps and leaf axils. Aedes aegypti was the most common in the city, breeding predominantly in discarded tyres, cement tanks and used battery boxes. Both Aedes aegypti and Aedes albopictus were resistant to dichlorodiphenyltrichloroethane (DDT; 4%), but susceptible to malathion (5%), and exhibited a varied response to pyrethroids. However, larval populations of both these mosquito species were susceptible to larvicides, including malathion (1.0 mg/L), temephos (0.02 mg/L) and fenthion (0.05 mg/L), at much lower dosages than diagnostic concentrations.

CONCLUSION

Given the seasonal abundance and case incidence in city areas, it is highly probable that Aedes aegypti is the predominant mosquito vector transmitting dengue virus. The study results have direct relevance for the state dengue-control programme, for targeting interventions and averting outbreaks and spread of disease.

Therapeutic efficacies of antimalarial drugs in the treatment of uncomplicated,Plasmodium falciparummalaria in Assam, north-eastern India

In the Indian state of Assam, the current therapeutic efficacies of the drugs commonly used in the area for the treatment of uncomplicated, Plasmodium falciparum malaria were investigated. As is routine in this area, subjects found positive for P. falciparum malaria were initially treated with chloroquine (CQ). They were given sulfadoxine-pyrimethamine (SP) if this treatment failed, and subsequently quinine if the SP failed. The protocol of the World Health Organization's extended in-vivo test was used to follow parasite clearance and clinical cure. Therapeutic response was assessed by comparing the baseline (day-0) level of parasitaemia with that observed on day 3. Many (75.7%) of the 144 evaluable subjects were treatment successes after CQ, but six early (4.2%) and 29 (20.1%) late CQ-treatment failures were observed. Of the 34 CQ-treatment failures followed, 31 (91.2%) responded adequately to SP but the other three were early (one) or late (two) SP-treatment failures. Two (66.7%) of the SP-treatment failures responded adequately to parenteral quinine but the other (a late quinine-treatment failure) had to be given an artemisinin derivative to achieve a clinical cure. The foci in which multidrug-resistant cases of malaria are developing in India need to be identified quickly, so that such cases can be cured before the mutant strains of P. falciparum that are resistant to several drugs have a chance to become more widespread.

Laboratory wash-resistance and field evaluation of deltamethrin incorporated long-lasting polyethylene netting (Netprotect(®)) against malaria transmission in Assam, north-east India

North-east India is co-endemic for Plasmodium falciparum and P. vivax malaria, and disease transmission is perennial and persistent. This study reports the results of a field-based village scale trial of deltamethrin incorporated long-lasting polyethylene netting (Netprotect(®)) conducted in P. falciparum predominant pocket of Assam, north-east India to assess operational feasibility, acceptability and sustainability against disease vectors and malaria transmission. The study monitored the residual efficacy of the long-lasting net in relation to serial washings in the laboratory and malaria prevalence in experimental villages for the first year of investigations from September 2008 to June 2009. The mosquito vector populations of Anopheles minimus were observed to be highly susceptible to deltamethrin (0.05%), and follow up investigations revealed that the vector mosquito had virtually disappeared in Netprotect(®) intervention villages. Concurrently, there was consistent decline in malaria cases in Netprotect(®) villages and transmission reduction was statistically significant compared to untreated net (net without insecticide) and no-net control villages for the corresponding study period. The contact cone-bioassay investigations against malaria transmitting mosquito species revealed that the bioavailability of the insecticide on the net fiber was persistent up to 20th serial wash resulting in ≥80% mortality. Community compliance and acceptance were high, and users reported decreased nuisance due to biting mosquitoes. It was concluded that deltamethrin incorporated polyethylene long-lasting netting was safe, wash-resistant, and assessed to be an operationally feasible, community-based intervention for sustainable management of disease vectors to prevent malaria transmission.

Malaria transmission and disease burden in Assam: challenges and opportunities

Malaria is major public health illness in Assam and 30-40% of the population is estimated to be at high-risk. Despite decades of attempted control interventions, malaria transmission is perennial and persistent in most parts of the state mostly transmitted by Anopheles minimus. Malaria outbreaks are returning associated with high rise in Plasmodium falciparum and attributable death cases. Therapeutic efficacy investigations for treatment of malaria revealed that chloroquine resistance was widespread for which artemisinin-based combination therapy (ACT) is being instituted in the control program. For data based on the preceding years, we briefly reviewed the available information on transmission dynamics, vector biology and control, drug policy, and discuss the challenges and opportunities for strengthening interventions for malaria control to help design situation specific strategies to check impending disease outbreaks with special reference to Assam. Under increased assistance from external agencies, we strongly advocate scaling up interventions based on mass distribution of long-lasting insecticidal nets (LLINs) for prevention and ACTs for treatment of drug-resistant malaria, and developing strong health delivery system in high-risk areas for meeting the complex emergencies and achieving transmission reduction.

Wash resistance and residual efficacy of long-lasting polyester netting coated with alpha-cypermethrin (Interceptor) against malaria-transmitting mosquitoes in Assam, northeast India

Malaria is endemic in Assam, northeast India, with low-to-moderate transmission of the causative parasites, mostly by Anopheles minimus. Plasmodium falciparum is the predominant parasite (>60%), with remaining cases being due to P. vivax. As an alternative intervention for malaria control, long-lasting insecticidal nets [Interceptor coated with alpha-cypermethrin 10% suspension concentrate (SC), 0.667% w/w, 0.2g/m(2)] underwent field evaluation for laboratory wash resistance and residual efficacy in field conditions against malaria-transmitting mosquitoes. Based on entomological observations, the Interceptor net intervention was the most effective, corresponding to the lowest mosquito vector density in experimental villages. There was virtual disappearance of A. minimus in Interceptor net villages in contrast to the untreated net intervention and the no-net control. Contact cone bioassay tests revealed 100% mortality in the A.minimus group of mosquito species in the community using the Interceptor net, which was consistent during the follow-up monitoring period (October 2006 to April 2007) in field conditions. Similar levels of mortality were observed in laboratory-washed nets compared with unwashed nets, and wash resistance was consistent even after the 20th serial wash at fortnightly intervals. Community compliance and acceptance of the Interceptor net was high, with decreased nuisance due to biting mosquitoes and other household insect pests being reported.

Complex population history of two Anopheles dirus mosquito species in Southeast Asia suggests the influence of Pleistocene climate change rather than human-mediated effects

Anopheles dirus and Anopheles baimaii are closely related species which feed on primates, particularly humans, and transmit malaria in the tropical forests of mainland Southeast Asia. Here, we report an in-depth phylogeographic picture based on 269 individuals from 21 populations from mainland Southeast Asia. Analysis of 1537 bp of mtDNA sequence revealed that the population history of A. baimaii is far more complex than previously thought. An old expansion (pre-300 kyr BP) was inferred in northern India/Bangladesh with a wave of south-eastwards expansion arriving at the Thai border (ca 135-173 kyr BP) followed by leptokurtic dispersal very recently (ca 16 kyr BP) into peninsular Thailand. The long and complex population history of these anthropophilic species suggests their expansions are not in response to the relatively recent (ca 40 kyr BP) human expansions in mainland Southeast Asia but, rather, fit well with our understanding of Pleistocene climatic change there.

Variation in the histopathological features of patients with ascending aortic aneurysms: a study of 111 surgically excised cases

Background:

Ascending aortic aneurysms (AA) are a common, though poorly understood medical condition.

Aims:

To document the histological changes in a large series of human ascending AA, and to correlate these changes with clinical variables.

Methods:

111 ascending AA were excised at surgery over a 3 year period. Each aneurysm was received as a continuous ring of tissue. Sections were taken from the anterior, posterior, greater and lesser curvature of the aorta and graded in a semi-quantitative fashion for the degree of elastin fragmentation, elastin loss, smooth muscle cell (SMC) loss, intimal changes and inflammation.

Results:

Mean patient age at surgery was 58.7 (15.6) years; there were 70 men and 41 women. 12 patients had Marfan syndrome, 34 (30.6%) had a bicuspid aortic valve (BAV), while 71 (64.0%) had a tricuspid aortic valve (TAV). Inflammatory cells were present in 28 cases (25.2%) and were confined to the adventitia. No particular region of the aortic circumference was more severely affected, however a BAV was associated with significantly less intimal change, and less fragmentation and loss of elastic tissue compared with patients with a TAV. Advanced age (>65 years), female gender and Marfan syndrome were all associated with more severe elastin degeneration and smooth muscle cell loss (p<0.05 for all).

Conclusion:

Results indicate a wide variation in the histological appearance in ascending AA, depending on patient characteristics. They suggest that the underlying aneurysm pathogenesis may also be highly variable; this warrants further investigation.

Malaria parasite burden and treatment seeking behavior in ethnic communities of Assam, Northeastern India

OBJECTIVES

The objectives of the study were to define the infectious reservoir of malaria with particular reference to transmission dynamics of Plasmodium falciparum, and to ascertain the disease trends in view of the existing containment practices and treatment seeking behavior in malaria endemic communities of Assam, India.

METHODS

Cross-sectional surveys were conducted in population groups of malaria endemic districts of the state to determine parasite prevalence, and data were analysed retrospectively for the years 1991-2003 to ascertain the disease trends. Structured questionnaire based surveys were conducted to study the treatment seeking behavior and practices of healthcare providers.

RESULTS

P. falciparum and P. vivax were the only two parasite species encountered, the former being in the majority (>60%). Malaria transmission was persistent, and a seasonal peak of P. falciparum was consistently observed during the months of heavy rainfall (April to September). Among children (5-15 years) there was a significantly higher malaria parasite rate as compared to the <5 years age group and adults (>15 years). There was a decline in parasite rates for all age groups over the years of the study that could not be attributed to vector control intervention intensities and/or meteorological factors.

CONCLUSIONS

The persistence of P. falciparum is attributed to the emergence of drug resistant varieties, inadequate interventions and treatment seeking patterns, and for its containment focused intervention measures are advocated in partnership with the communities.

Transmission of malaria and its control in the northeastern region of India

Let alone the eradication, malaria control itself has amounted to be a challenge, and is detrimental to the all round development of the northeastern region of India. Focal outbreaks are frequent taking heavy tool on human lives. Plasmodium falciparum is the predominant parasite species and is solely responsible for increased morbidity and mortality. The region contributes bulk of P. falciparum cases for the rest of India, and its proportions are increasing. Efficient vectors like Anopheles minimus, Anopheles fluviatilis and Anopheles dirus persistently support transmission of malaria. The present review gives a comprehensive account of the factors responsible for transmission of the disease with focus on vector bionomics, its prevention and control.

Allelic variation in the cg2 gene does not correlate with chloroquine resistance among Indian Plasmodium falciparum isolates

The cg2 gene of Plasmodium falciparum has been proposed to be associated with chloroquine resistance. Here we describe PCR amplification and sequencing of all the four repeat regions (kappa (kappa), gamma (gamma), psi (psi) and omega (omega)) of this gene, from Indian isolates. There were variant forms for each of these repeat regions (two for kappa and gamma, and three for psi and omega) among the 123 Indian isolates of P. falciparum. Among these isolates certain forms of psi and omega repeats were uniquely present while some of the reported forms of the kappa and omega repeats were absent. The pattern of combination of all four repeat regions of cg2 gene (genotype) was analysed from 52 isolates. A total of 11 different genotypes were observed among these cases, of which 10 were unique to Indian isolates. Certain genotypes were more common than others. The nucleotide sequencing of all the four repeat regions revealed that Indian isolates have some unique repeating units within the gamma and omega domains. Altogether, the PCR and sequencing results showed that there was an unrelatedness between cg2 repeats and chloroquine resistance.

Multicentric clinical trials for safety and efficacy evaluation of alpha;beta arteether in complicated P. falciparum malaria

OBJECTIVE

To evaluate efficacy of alpha;beta arteether in patients of P. falciparum malaria presenting with complications was undertaken in a multicentric clinical trial.

METHOD

Each patient who consented to undergo clinical trial with parenteral Arteether was treated with a fixed dose schedule of Arteether given intramuscularly in a dose of 150 mg once a day on three consecutive days. Every patient was followed upto 28 days with clinical, haematological and parasitological monitoring every day upto one week and thereafter at 14, 21 and 28 days. The response was assessed in terms of fever clearance time, parasite clearance time, cure rate and parasite reappearance rate.

RESULTS

A total of 211 patients of P. falciparum malaria were included in the study from four centres (Bhilai, Guwahati, Jamshedpur and Rourkela). Results of this study showed that fever clearance time ranged between 24-168 hours, parasite clearance time ranged between 24-120 hours and overall mortality ranged between 4-8.5%. Out of 211, only 14 patients expired during the study, of these, 10 patients expired within first two days i.e. before completing the three day schedule of arteether therapy. Tolerability to arteether injection was good in all these patients and no untoward effects were experienced or reported during the study. Overall cure rate observed in these studies was 93%.

CONCLUSION

This study shows a rapid parasite and fever clearance in patients of complicated P. falciparum malaria.

Malaria-attributable morbidity in Assam, north-eastern India

Malaria is endemic in the Indian state of Assam and transmission of the causative parasites is perennial and persistent. The available data on malaria-related morbidity and mortality in the state for the years 1991-1999 have been reviewed. Over this period, Plasmodium falciparum was the predominant parasite, causing 58%-68% of the malaria cases; all other cases were attributed to P. vivax. All malaria-related deaths were attributed to P. falciparum infection, and the numbers of such deaths were correlated with the numbers of cases of P. falciparum malaria. The deaths occurred mostly in the rainy season (April-September) and among all age-groups of both sexes. The factors responsible for focal outbreaks of malaria across the state are discussed in relation to the existing health infrastructure.

An outbreak of Plasmodium falciparum malaria due to Anopheles minimus in central Assam, India

Epidemiological investigations were conducted in Nellie subcentre, PHC Jhargaon, under Morigaon district (Assam). The results of fever cases revealed 68 per cent slide positivity rate (SPR) and 40 per cent slide falciparum rate (SfR). The Pf proportion was > 87 per cent and remaining cases were P. vivax infections. An. minimus was incriminated as a malaria vector during the study period. The sporozoite rate was 3.08 per cent. The indoor man mosquito contact was 35 per bait/night as against 23 in outdoors. Results of susceptibility test revealed that the vector was still susceptible to both DDT and malathion at discriminating dosages. The study revealed that inadequate surveillance and vector control measures were contributing factors for malaria outbreak. In view of this, insecticide treated nets may be introduced to provide cost-effective control of malaria.

Quetiapine: a review of its safety in the management of schizophrenia

Quetiapine, a dibenzothiazepine derivative, is a atypical antipsychotic which has greater in vitro binding affinity for serotonin 5-HT2 receptors than for dopamine D2 receptors. Quetiapine effectively treats both the positive and the negative symptoms of schizophrenia and is also associated with an incidence of extrapyramidal symptoms no greater than placebo across the entire dose range. In addition, it does not cause persistent hyperprolactinaemia. Quetiapine is associated with high levels of patient acceptability and satisfaction, which may result from its combination of efficacy and relatively benign adverse effect profile. The drug is well tolerated and has a low propensity to cause adverse events both during acute and long term treatment in the adult populations. The adverse effect profile of quetiapine makes the drug advantageous for patient populations who are susceptible to the adverse effects of drugs. Indeed, preliminary data show quetiapine to be very well tolerated in the elderly. Overdoses of quetiapine of up to 20g have been reported; however, with appropriate management in an intensive care setting there have been no reported fatalities. Quetiapine is metabolised by the cytochrome P450 3A4 isoenzyme, and the dose may need to be adjusted if quetiapine is co-administered with drugs which affect the activity of this isoenzyme. Overall, quetiapine has a favourable risk-benefit profile that should make it a valuable first-line agent in the treatment of schizophrenia.

Complicated appendicitis: is there a minimum intravenous antibiotic requirement? A prospective randomized trial

The proper duration of postoperative intravenous (IV) antibiotics in patients suffering complicated (perforated or gangrenous) appendicitis is debatable. Some advocate a set minimum number of IV antibiotic days whereas others discontinue IV antibiotics depending on the patient's clinical course regardless of the length of therapy. Our objective was to determine whether there are differences in morbidity and resource utilization between the two treatment methodologies. Ninety-four patients with intraoperative findings of complicated appendicitis were included. In all patients IV antibiotics were discontinued on the basis of clinical factors. However, Group 1 patients were given a minimum 5-day IV antibiotic course whereas Group 2 patients had no minimum IV antibiotic requirement. Group 1 patients received more IV antibiotics than Group 2 patients did (5.9 vs 4.3 days; P = 0.014). Infectious complications were not statistically different between the two groups (13.0% in Group 1 and 12.5% in Group 2). Average hospital stay was also not statistically different between the two groups. The data suggest that a protocol with no minimum IV antibiotic requirement in patients with complicated appendicitis does not increase morbidity. Furthermore, the protocol arm with no minimum IV antibiotic requirement led to less IV antibiotic use but did not significantly decrease hospital stay.

Cytotaxonomic evidence for the presence of Anopheles nivipes in India

Anopheles philippinensis mosquitoes were collected from 5 states in India: Assam, Meghalaya, Arunachal Pradesh, Manipur, and Nagaland. Half-gravid females were examined for variations in wing venation using the presector dark mark on vein I and polytene chromosomes derived from ovarian nurse cells. Polytene chromosomes were examined for diagnostic inversions, t on chromosome arm 2 and I on arm 5. Based on wing characteristics, both An. philippinensis and An. nivipes were identified. Polytene chromosome examinations revealed that all specimens from these 2 populations had 2t; 51 inversion genotype, a diagnostic character for An. nivipes. The wing character was not diagnostic; therefore, it was concluded that all the specimens examined were actually An. nivipes and not An. philippinensis. Further, the X chromosome was of x+b type, that is, the standard arrangement with reference to the inversion b, reported in the An. nivipes population in Thailand. This is the 1st report that unequivocally establishes the occurrence of An. nivipes in India and also shows that the adult wing character is not reliable in distinguishing An. philippinensis from An. nivipes, as has been observed in Thailand.

Juvenile tricuspid stenosis and rheumatic tricuspid valve disease: an echocardiographic study

Tricuspid valve involvement is not uncommon in patients with rheumatic heart disease and is frequently missed on routine clinical examination. We prospectively studied the echocardiographic profile of tricuspid valve disease in 788 consecutive patients with rheumatic heart disease. Out of these patients 9% (70) had tricuspid valve disease and 55.7% (39) of these were of < or = 20 years of age. Of these 60% were females and 40% were males. Their ages ranged from 9 to 64 years (mean 24.2+/-13.6 years). Of these patients, 50% had tricuspid stenosis with or without tricuspid regurgitation whereas 50% had isolated tricuspid regurgitation. Isolated tricuspid stenosis was present in 7.4% of these cases. All patients had associated mitral stenosis. Severe mitral stenosis was present more commonly in patients with juvenile tricuspid stenosis compared to older patients (94.1% vs. 55.6%, P<0.005). Mitral regurgitation was present more commonly in juvenile age group patients compared to older patients (53.8% vs. 25.8%, P<0.01). A combination of mitral, aortic and tricuspid stenosis was present in five cases and four of these were in the juvenile age group. Left ventricular enlargement and dysfunction were present in 28.6 and 14.3% patients, respectively, and the majority of these patients were in the juvenile age group (P<0.05). We conclude that rheumatic tricuspid valve disease occurs early in the course of the disease and progresses faster in India and is always associated with mitral stenosis. Juvenile tricuspid stenosis is more commonly associated with severe mitral stenosis, mitral regurgitation, left ventricular enlargement and dysfunction as compared with older patients.

Sustained local drug delivery to the arterial wall via biodegradable microspheres

This study was designed to evaluate the feasibility of applying locally delivered polylactic acid microspheres for drug delivery to the arterial wall. To study drug persistence, rhodamine-loaded microspheres were infused into one carotid artery of 14 rabbits and plain rhodamine solution into the other by using a porous balloon. To study tissue response, plain microspheres and dexamethasone-loaded microspheres were infused into the carotid arteries of another group of rabbits. To study the antiproliferative effects of locally delivered drug, 20 rabbits were subjected to overstretch balloon injury to both carotid arteries and divided into 4 groups: injury alone, plain microspheres, dexamethasone-loaded microspheres, and microspheres containing colchicine and dexamethasone. Fluorescent microspheres persisted in the vessel wall for 4 wk, whereas rhodamine without microspheres disappeared at 72 h. Histopathologic studies in arteries infused with unloaded microspheres showed inflammatory cell infiltrate with polymorphonuclear cells at 1 wk and macrophages and giant cells at 4 wk. Arteries infused with dexamethasone-loaded microspheres did not show any inflammatory cell infiltrate. Local delivery of dexamethasone or dexamethasone plus colchicine did not result in significant change in the intima-to-media ratio or in residual lumen following balloon injury. Polylactic acid microspheres may be used for prolonged delivery of drugs or other bioactive agents locally to the arterial wall. They induce an inflammatory reaction that is suppressable by dexamethasone in the microspheres. Dexamethasone or dexamethasone and colchicine delivered via this system, however, failed to reduce the degree of intimal hyperplasia after overstretch balloon injury to the rabbit carotid arteries.

Effect of the balloon-anulus ratio on the intermediate and follow-up results of pulmonary balloon valvuloplasty

Pulmonary balloon valvuloplasty (PBV) is an effective method to treat congenital valvular pulmonic stenosis, but the ideal balloon-anulus ratio (BAR) for this procedure remains unclear. We studied 71 procedures where BARs of 1.0-1.5 were used, since it has been shown that a ratio of < 1.0 is less effective and that of > 1.5 may produce more complications. A curvilinear relation was found between BAR and the fractional fall in haemodynamic parameters reflecting stenosis severity, both immediately after dilatation and at follow-up. Best results were observed with a BAR of 1.25, with progressive worsening on either side of this ratio. The relationship remained significant in multiple regression analysis involving age, sex and baseline haemodynamic variables. The data show that a BAR of 1.25 is probably the ideal ratio for PBV.

Subacute thrombosis and vascular injury resulting from slotted-tube nitinol and stainless steel stents in a rabbit carotid artery model

BACKGROUND

Our objectives were to quantify the thrombogenicity and extent of vascular injury created by slotted-tube geometry stainless steel and nitinol coronary stents in a rabbit carotid artery model.

METHODS AND RESULTS

Stents were implanted in rabbit right carotid arteries without antiplatelet therapy. Stainless steel stents were implanted for 4 days while nitinol stents were placed for 4 and 14 days (n = 8, 8, and 6, respectively). Stent thrombosis was assessed by thrombus weight, grading thrombus encroachment of the lumen, and by blood flow in the stented and contralateral arteries. Stainless steel stents at 4 days contained more thrombus than 4- and 14-day nitinol stents (20.0 +/- 5.9 versus 2.5 +/- 0.6 and 2.7 +/- 0.3 mg, respectively; P < .000001). Stainless steel stents were more often occluded by thrombus (6 of 8) or contained more subocclusive thrombus (2 of 8) than nitinol stents (0 of 14, P < .002). Resting blood flow was reduced in arteries with stainless steel stents compared with 4- and 14-day nitinol stents (1.5 +/- 2.8 versus 24.0 +/- 2.0 and 25.5 +/- 1.9 mL/min, respectively, P < .000001). Stainless steel stents were less uniformly expanded, had deeper strut penetration into the vascular wall, and were associated with more extensive medial smooth muscle cell necrosis. There were strong correlations (r = .77 to .95) between variables of thrombosis extent (thrombus weight and grade) and histologically determined vascular injury (strut penetration and medial necrosis).

CONCLUSIONS

Slotted-tube stainless steel stents were more thrombogenic and created more extensive vascular injury than nitinol stents in a rabbit carotid artery model. The mechanisms underlying these differences probably are related to metallurgic and design geometry properties of the two stent types.

Morbidity and mortality due to malaria in Tarajulie Tea Estate, Assam, India

Beginning 1991, a sudden rise of malaria cases were recorded in Tarajulie TE (Assam) coupled with mortality due to malaria. Deaths were confirmed due to Plasmodium falciparum (Pf) infections and were recorded in all age groups excluding infants. Malaria positives were recorded in all months of the year, however, there was a increased hospital attendance due to fever/malaria positives during May to September. During the years (1991-1993), the slide positive rate was as high as 33.04%, mostly being Pf infections (69%), and the annual parasite index ranged between 6 to 304 per thousand population. Morbidity and mortality due to malaria were attributed to labor movements to and fro from garden premises to adjoining hamlets, the latter being the site of acquisition of the infections.

Malaria survey in Tarajulie tea estate and adjoining hamlets in Sonitpur District, Assam

Malaria survey in Tarajulie tea estate (TE) and its adjoining hamlets revealed that Pf was the predominant parasite species (79%) and morbidity was alarming. Malaria positive cases were recorded in all age groups including infants. However, morbidity was much pronounced in the hamlets than among garden dwellers. Mostly Anopheles minimus were recorded in the day resting collections from human dwellings (indoor) and in overnight man biting catches in the hamlets. From these collections. An. minimus was incriminated and the sporozoite infection rate was found to be 4.23 per cent. An. minimus were not recorded in the garden premises. Thus morbidity in the garden population was attributed to the movement of labourers to and fro between hamlets and the garden premises. The hamlets served as reservoirs for malaria infection.

Anopheles minimus: its bionomics and role in the transmission of malaria in Assam, India

Indoor, day-resting collections of Anopheles minimus mosquitos from human dwellings in the study area in Assam, India, indicated that these insects were prevalent throughout the year and that their maximum abundance occurred from March to August. A. minimus was identified as a vector of malaria, and sporozoite infections were recorded every month of the year, with the highest rating occurring in October. The mosquito was highly anthropophilic and fed on human hosts (indoor) all through the night, but feeding was more pronounced between 01:00 and 04:00, the person-biting rate was 13.7 per night. Breeding occurred throughout the year in slow-flowing streams with grassy banks. A. fluviatilis was also identified as a vector of malaria in the study area but occurred in low density, and sporozoite infections were only seasonal.

Susceptibility of Plasmodium falciparum to chloroquine in tea garden tribes of Assam, India

P. falciparum was the predominant parasite ( > 80%) species in malaria ridden tea estates of Assam. A simplified 3 day in vivo test to determine chloroquine sensitivity in tea garden tribes revealed that the majority of the cases (85%) were S/RI, 7% were RI, and 3% were RII and 5% were RIII, respectively. Early case detection and treatment were deemed necessary to reduce morbidity and mortality due to P. falciparum in these tea estates.

Deltamethrin impregnated bednets against Anopheles minimus transmitted malaria in Assam, India

Of the 20 Anopheles species caught in villages in Sonapur, Assam, only An. minimus was incriminated as a malaria vector by finding sporozoites in the salivary glands. It was found to be endophagic and endophilic in Assam and because its biting peaked after midnight it was a suitable target for insecticide impregnated bednets. After the withdrawal of DDT spraying and collecting a year's baseline data, deltamethrin impregnated nets were distributed in 3 villages, untreated nets were distributed in 6 villages and 3 were held as untreated controls. The population of each of these groups of villages was about 1700. The nets were well received by the local tribal population. Human landing catches with baits unprotected or under partially lifted nets showed that the nets provided a high degree of personal protection against all the local species of human biting mosquito. In addition, there was evidence for suppression of the An. minimus population in a village with treated nets. Malaria was monitored by weekly active surveillance in all the villages. In the untreated control villages the slide positivity rate and monthly parasite index rose significantly during the trial. In the villages with untreated nets, these parameters showed no significant change, but in the villages with treated nets they declined significantly. On the basis of these results, the widespread distribution of impregnated nets was recommended to the state health authorities.

Kinetics of drug delivery to the arterial wall via polyurethane-coated removable nitinol stent: comparative study of two drugs

Polymer-coated removable stents were used to deliver 14C-labeled etretinate and 3H-labeled forskolin to the vessel wall in 31 New Zealand White rabbits to study their kinetics. Stents loaded with etretinate (n = 8) and forskolin (n = 14) were implanted in the rabbit carotid arteries, and the animals were euthanized at different time intervals. Drug levels were measured in the media and adventitia of the stented segment, in distant tissues, and in blood. In four rabbits, forskolin-loaded stents were percutaneously retrieved 2 hr after implantation in the carotid artery, and the tissue and blood levels were determined 2 and 24 hr after retrieval. In seven rabbits etretinate-loaded stents were retrieved 72 hr after implantation in abdominal aorta, and drug levels were measured in the tissues and blood immediately after and at 1 and 4 days after retrieval. Levels of etretinate in the vessel wall peaked at 24 hr (250 ng/mg) and remained high up to 72 hr (185 ng/mg) after stent placement. Levels of forskolin peaked within 2 hr of stent placement (135 ng/mg) and rapidly declined to 4.9 ng/mg at 24 hr with the stent in situ. About 50% (1.4 mg) of the original etretinate remained in the stent at 72 hr compared to about 5% (0.08 mg) of forskolin at 24 hr. Ratio of peak drug levels in the vessel wall to those in the blood was 6,000 for etretinate and 780 for forskolin. (ABSTRACT TRUNCATED AT 250 WORDS)

Localized arterial wall drug delivery from a polymer-coated removable metallic stent. Kinetics, distribution, and bioactivity of forskolin

BACKGROUND

Coronary stenting is associated with two major complications: subacute thrombosis and neointimal proliferation resulting in restenosis. Our hypothesis is that the biocompatibility of metallic stents can be improved by coating with a polymer membrane that delivers agents that favorably modify the local arterial microenvironment. This study evaluates the kinetics, distribution, and bioactivity of the model drug forskolin delivered to the local arterial wall by a polyurethane-coated removable metallic stent.

METHODS AND RESULTS

Stents were used in rabbit carotid arteries (n = 20) for as long as 24 hours. The quantity of forskolin bound to the stent decreased exponentially with a half-life of 5.8 hours. Blood concentrations peaked at 140 +/- 39 pg/microL at 4 hours. The adjacent arterial media contained 60 +/- 39 ng/mg, which was 380- and 460-fold greater than the contralateral carotid media and the systemic blood, respectively (P < .0001). Media forskolin concentrations declined exponentially over time with a tissue half-life of 5.0 hours. Drug distributed throughout the vessel wall with decreasing gradients in the radial and axial dimensions consistent with a diffusion process. Removal of the stent was associated with a 100-fold decline in media forskolin concentration within 2 hours. Forskolin release was associated with a sustained 92% increase in carotid blood flow and a 60% decrease in local arterial resistance compared with coated control stents (P < .005). In another set of rabbits (n = 14) using a carotid crush injury, flow-reduction model, forskolin prolonged the time to flow variation and occlusion by 12-fold compared with the use of bare metal stents and 5-fold compared with the use of polyurethane-coated stents (P < .0001).

CONCLUSIONS

A polymer-coated metallic stent can deliver forskolin to the local arterial wall in high concentrations relative to the blood or other tissues. High local drug concentrations are dependent on maintaining stent-to-tissue gradients. The delivered drug is biologically active, demonstrating vasodilating and antiplatelet properties.

Current status and prospects for the use of temporary stents

Temporary stenting appears to be an attractive potential therapy that combines some of the benefits of permanent stenting without the need for permanent endovascular prostheses and oral anticoagulation. The devices used for temporary stenting are still evolving. The Flow Support Catheter showed promise in the early clinical trial phase but is not being pursued by the original manufacturer because the device was associated with a high rate of thrombosis and suboptimal overall success rate. The experience with the Instent is limited and the removal of its unattached version relies upon catching the end of the stent in the retrieval device (a wire loop); also, its safety and reliability still need to be proved. The HARTS device is currently in the preclinical phase, but available data from animal studies show it to be a feasible device for coronary use. Its potential applications include use as a permanent stent, a temporary stent, a repositionable stent, a primary lesion-dilating device, or a local drug-delivery vehicle. Clinical trials are likely to commence in the foreseeable future for one or more of these applications.

A follow up study of major intimal dissections treated with perfusion balloon catheter

Major intimal dissections during coronary angioplasty are an important cause of early morbidity and mortality. In the recent past various non-surgical modalities to manage such dissections have been developed. The choice of therapy among these needs knowledge not only of immediate success but also of long term results. Data on long term follow up of patients managed with prolonged balloon inflations using a perfusion balloon catheter is limited. We herein report our experience of twenty seven consecutive patients managed by prolonged dilatations using Stack perfusion balloon catheter. All the patients had a long dissection with luminal compromise, 6 (22%) had in addition an acute complete occlusion, and in 4 (15%) there was a thrombus. Only 6 (22%) needed an emergency CABG, with the remaining having an event free hospital stay. At follow up after 6-26 months, 7/21 (33%) had severe symptoms and 5 of them underwent coronary arteriography with four having a repeat successful dilatation. The findings of this study suggest that the perfusion balloon catheter is a useful modality for management of major dissections with a restenosis rate similar to that of primary PTCA. Randomised controlled trials are required to assess its efficacy vis a vis the newer therapeutic options like stents, lasers and atherectomy.

Percutaneous balloon mitral valvuloplasty: analysis of echocardiographic and other variables related to outcome

To determine whether mitral valve (MV) morphology influences the result of balloon mitral valvuloplasty (BMV) for mitral stenosis, two-dimensional echocardiography was performed before BMV in 53 patients and in 25 normal controls. The two-dimensional echocardiographic features of MV leaflets: thickness, length and motion, diastolic MV excursion, chordal length, MV annular diameter (MVAnD), subvalvular distance ratio (SDR), and effective balloon dilating area (EBDA) and diameter (EBDD) were then correlated to the immediate post-BMV mitral valve area (MVA). For the total patient population, post-BMV MVA increased from 0.76 +/- 0.24 to 1.91 +/- 0.59 cm2 (p < 0.0001) and mean diastolic transmitral gradient decreased from 20.1 +/- 6.15 to 5.8 +/- 3.29 mm (p < 0.0001). The patients were divided into two groups on the basis of post-BMV MVA. Group I had post-BMV MVA < 2.0 cm2 and group II had post-BMV MVA > or = 2.0 cm2. A statistically significant difference was noted in SDR (0.33 +/- 0.057 vs 0.45 +/- 0.042, p < 0.0001); mid-MV anulus to tip of papillary muscle (PM) distance (20.0 +/- 3.8 vs 27.9 +/- 4.54 mm, p < 0.0001); chordal length (4.3 +/- 3.6 vs 9.8 +/- 3.9 mm, p < 0.0001); diastolic MV excursion (15.5 +/- 2.6 vs 18.2 +/- 4.2 mm, p < 0.01); leaflet mobility (p < 0.05); and EBDA (4.4 +/- 0.6 vs 4.9 +/- 0.5 cm2, p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)