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PubMed1997

What's new in malaria control?

Malaria remains a significant health problem in many tropical areas but the main impact of the infection is felt in sub-Saharan Africa, where malaria continues to cause many deaths and much morbidity. Recently, several new initiatives to improve malaria control in Africa have been started. Control is difficult to achieve in areas with very high levels of transmission but something can be accomplished with existing tools, which include provision of good treatment facilities, chemoprophylaxis in pregnancy and use of insecticide-treated materials. In some areas, especially on the fringes of sub-Saharan Africa, households spraying may also have a role. Use of insecticide-treated materials has had a major impact on child mortality in several countries in Africa, although there are concerns that the dramatic effects achieved initially may not be sustained. A major constraint on malaria control in Africa has been poor organization of malaria-control programmes. New approaches that combine elements of vertical and of horizontal control systems are being tried. Malaria control, even when carried out efficiently and cost-effectively, is relatively expensive. New ways of financing malaria control in the countries where it is needed most must be found.

Africa South of the Sahara↗
PubMed1997

Control of gastro-intestinal parasitism in sheep with ivermectin delivered via an intraruminal controlled-release capsule.

The efficacy of ivermectin delivered by an intraruminal controlled-release capsule against gastro-intestinal nematodes of sheep was evaluated under controlled conditions. In seven Australian studies involving 170 Merino or Merino x Border Leicester sheep, intraruminal capsules developed for 20-40 kg or 40-80 kg sheep, and delivering 0.8 or 1.6 mg of ivermectin/day respectively for 100 days (minimum dose 20 microg/kg/day), were evaluated. Studies were designed to test the therapeutic efficacy against naturally acquired and induced infections treated at the adult and fourth larval stage, and the prophylactic efficacy against naturally acquired and induced infections with third stage infective larvae. The predominant pathogenic nematodes of sheep were represented. Two studies included known benzimidazole- and levamisole-resistant nematode strains. Sheep were necropsied for total nematode counts 21-8.5 days after treatment. The efficacy of the ivermectin controlled-release capsule was generally >99% against all nematode species tested, including those confirmed to be benzimidazole- and levamisole-resistant. High therapeutic activity was demonstrated against existing adult and fourth larval stage nematode infections at the time of treatment, and high prophylactic efficacy was shown against incoming third stage larvae of all species and strains tested.

Journal Article↗
PubMed2005

Targeting of mannosylated liposome incorporated benzyl derivative of Penicillium nigricans derived compound MT81 to reticuloendothelial systems for the treatment of visceral leishmaniasis.

The antileishmanial property of a Benzyl derivative of a new antibiotic MT81 (Bz2MT81), isolated and purified from a fungal strain of Penicillium nigricans NRRL 917 was tested in free, liposome intercalated and mannose coated liposome intercalated forms in vivo against visceral leishmaniasis in hamsters. Mannose grafted liposome intercalated Bz2MT81 eliminated intracellular amastigotes of Leishmania donovani within splenic macrophages more efficiently than the liposome intercalated Bz2MT81 or free Bz2MT81. At a dose equivalent to 7.5 microg/Kg body weight when injected subcutaneously (s.c) in mannose grafted liposome intercalated form for 15 days in an interval of three days, the splenic parasitic load decreased to the extent of 79.1% of the total parasite present in infected control animals. Whereas, an identical amount (7.5 mug/Kg body weight) of Bz2MT81 in free or liposome intercalated form was found less effective in controlling the parasite in spleen (in free Bz2MT81 form, suppression of parasitic load is 49.8% and in liposome intercalated form, it is 55.1%). Both mannosylated liposomes and Bz2MT81 were noted non-toxic to the host peritoneal macrophages. Histological examinations of spleen and liver, kidney function tests (SGPT, alkaline phosphatase, creatinine and urea in blood plasma) showed that the toxicity of Bz2MT81 was reduced up to normal level when mannose grafted liposomal Bz2MT81 were administered.

Animals↗
PubMed1995

Knowledge of mosquitos in relation to public and domestic control activities in the cities of Dar es Salaam and Tanga.

A study of community awareness of mosquitos and related subjects in the residential areas of two Tanzanian cities (Dar es Salaam and Tanga) showed that residents were well aware of mosquitos. Almost all claimed to use some form of domestic mosquito control product for their personal protection, and many spend a significant portion of the household income on this. The problems of nuisance-biting and malaria transmission are usually not separated and are considered to be the result of poor environmental hygiene, for which both residents and local authorities are responsible. Although Culex mosquitos are not a primary target of the Urban Malaria Control Project (UMCP), the persistence of nuisance-biting has made residents sceptical and dissatisfied with insecticide spraying. The residents' priorities are evidently not the same as those of the health authorities, yet mutual cooperation is essential. In order to maintain community support, campaigns aimed at malaria vectors should consider the need for additional measures to control Culex mosquitos, such as those now being tried by the UMCP. Mosquito breeding sites are non-specifically associated with rubbish and standing water of all kinds, and so the actions that the community considers necessary for mosquito source reduction tend to be poorly targeted. Residents do not recognize that some sources produce malaria mosquitos while others produce nuisance mosquitos. The environmental anti-mosquito measures currently promoted by health education and other forms of propaganda are also poorly targeted. While some of them are directed at important Culex breeding sites, others are aimed at sites of little importance for mosquitos of any kind.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1996

From efficacy to effectiveness: insecticide-treated bednets in Africa.

Insecticide-treated bednets and curtains (ITBC) have proven in recent large-scale trials to have a high efficacy in reducing morbidity and mortality from malaria in African children. However, it is unlikely that the efficacy measured in trials can be entirely sustained under programme conditions. This has important implications for the cost-effectiveness of the intervention. Furthermore, there is a need to assess the long-term impact of ITBC. This article traces the history of ITBC and the different phases of their assessment, especially the determination of efficacy in randomized controlled trials (phase III assessment). It then outlines the reasons for continued assessment of their effectiveness under programme conditions (phase IV assessment). The methodologies for measuring effectiveness are discussed, and a critical review of the issues reveals that it is impractical to measure effectiveness directly. A simple effectiveness model, allowing for differentiation between individual and community effectiveness, provides a useful conceptual framework. First, individual effectiveness is measured through a case-control study. This estimate is then combined with a coverage indicator to estimate community effectiveness. This approach could provide programme managers with a powerful tool to monitor the impact of health interventions at the community level.

Africa↗
PubMed1999

A comparison of the bioequivalence of 0.5% fenbendazole top dress pellets or 10% fenbendazole oral suspension against a spectrum of equine parasites.

A controlled test was conducted to assess the efficacy bioequivalence of a single dose of 0.5% fenbendazole (FBZ) top dress pellets to a 10% FBZ suspension formulation (Panacur suspension 10%, Hoechst Roussel Vet). Thirty horses with naturally-acquired parasite infections, in replicates of three, were used. Strongyle egg per gram counts were not significantly different (P>0.1) between groups pretreatment, but FBZ treated groups were significantly different from the control group post-treatment. At necropsy, which occurred seven to nine days post-treatment, two methods of nematode recovery were compared to assess whether a small aliquot can be used in a control test to determine efficacy against large as well as small strongyles. Both post mortem worm recovery techniques revealed similar efficacies of both formulations (>95%) against small and large strongyles, but large differences in the number of worms recovered. Six species of small strongyles comprised 96% of all the small strongyles recovered: Coronocyclus coronatus, Cylicocyclus insigne, Cylicostephanus longibursatus, Cylicocyclus brevicapsulatus, Cylicocyclus nassatus, and Cyathostomum catinatum. The results of this study demonstrated therapeutic bioequivalence between FBZ formulations and also the need to sample at least a 10% aliquot to accurately estimate number of large strongyles. No adverse reactions to treatment were detected.

Administration, Oral↗
PubMed2006

The epidemiology of visceral leishmaniasis in Bangladesh: prospects for improved control.

The parasitic disease kala-azar (visceral leishmaniasis, VL) was first described in 1824 in Jessore district, Bengal (now Bangladesh). Epidemic peaks were recorded in Bengal in the 1820s, 1860s, 1920s, and 1940s. After achieving good control of the disease during the intensive vector control efforts for malaria in the 1950s-1960s, Bangladesh experienced a VL resurgence that has lasted to the present. Surveillance data show an increasing trend in incidence since 1995. Research in recent years has demonstrated the utility of non-invasive diagnostic modalities such as the direct agglutination test and rapid tests based on the immune response to the rK39 antigen. In common with its neighbours India and Nepal, VL in Bangladesh is anthroponotic. Living in proximity to a kala-azar case is the strongest risk factor for disease, while consistent use of bed nets in the summer months and the presence of cattle are protective. Shortages of first-line antileishmanial drugs and insecticide for indoor spraying programmes have hindered VL treatment and vector control efforts. Effective control of VL will require activities to improve availability and access to diagnostic testing and antileishmanial drugs, enhanced surveillance for kala-azar, post-kala-azar dermal leishmaniasis and VL treatment failures, and increased coverage and efficacy of vector control programmes.

Bangladesh↗
PubMed1992

Economic benefits of controlling internal and external parasites in South American camelids.

A trial was carried out in alpacas (Lama pacos) and llamas (Lama glama) to determine the economic benefits of controlling both external and internal parasites by the use of ivermectin ("Ivomec," Merck Sharp & Dohme). After four months the treated male alpacas gained on average 3.1 kg more than the untreated males, and their fleece weighed 0.36 kg more. The treated female alpacas gained 1.9 kg more than the controls, but their fleece weighed 0.03 kg less. This treatment gave a net financial benefit to the farmer of U.S. $3.54 for each of his male alpacas and U.S. $1.36 for each of his female alpacas. The results for the llamas were not significant because there was great variation in the weight gains (and losses). Because the value of llama fleece is less, the economic benefits were also less.

Animals↗
PubMed1998

Complex dynamic behaviours in the interaction between parasite population and the host's immune system.

The paper describes recent progress in the development of a mathematical framework for the study of epidemiology, evolution, within-host parasite population growth and the control of parasitic infections. A major emphasis is placed on dynamic models of the interaction between the parasite population and the host's immune system that capture the effects of antigenic variation, parasite evolution in response of immunological attack and the control of population growth by chemotherapeutic agents.

Animals↗
PubMed2006

Monomers of condensed tannins affect the larval exsheathment of parasitic nematodes of ruminants.

The current control of parasitic nematodes in small ruminants relies on the use of chemical anthelmintics, but the development of resistance requires research in alternatives. Bioactive plants represent one of those solutions. Previous results suggest that plants rich in condensed tannins (CTs) might have direct anthelmintic effects. However, the relationships between the biochemistry of active compounds and the mechanisms of action remain to be elucidated. Therefore, this study examined in vitro the effects of different CT monomers on the exsheathment of infective larvae for two nematode species. Monomers of prodelphinidins were more potent inhibitors of exsheathment than those of procyanidins. More severe inhibition was also found with galloyl derivatives. These results suggest that the number of free hydroxy groups of CT monomers is a key factor in interactions with parasite larvae. Comparison of effects between the two nematodes suggests different susceptibility to monomers depending on species, which might be related to the protein composition of sheaths.

Animals↗
PubMed1999

Implementing a malaria curtains project in rural Malawi.

This paper describes planning, implementation, monitoring and evaluation activities carried out in support of a malaria control project that used permethrin-impregnated curtains in eight villages in rural Malawi. Findings from formative evaluation and project monitoring aspects of the evaluation are presented. Permethrin-impregnated curtains were introduced to villagers who participated in household self-help projects. To implement the project, village health workers were trained and worked closely with existing project personnel as well as traditional headmen to assure village participation, facilitate health education and coordinate curtain-dipping (impregnation) meetings. A quasi-experimental evaluation design used surveys and observations to measure change in cognitive, behavioural and health outcome indicators. Village adoption rates averaged 50%, with variation between villages. Monitoring data showed a high degree of compliance with curtain re-impregnation initially and high perceived efficacy of curtains. Issues discussed include village readiness for change, trust, acceptability of the innovation, cost, sustainability and leadership.

Attitude to Health↗
PubMed2000

Efficacy of an ivermectin controlled-release capsule against some rarer nematode parasites of sheep.

A controlled trial was conducted to evaluate the efficacy of the intraruminal ivermectin controlled-release capsule (CRC) (IVOMEC Maximizer CR Capsule for Sheep, Merial Ltd.) against induced incoming third-stage larvae and established adult infections with some rarer gastrointestinal nematode parasites of sheep. Twenty-one worm-free lambs were allocated by restricted randomisation based on body weight within sex to one of the following treatments: unmedicated control, ivermectin CRC given on Day 0 prior to induced infection, and ivermectin CRC given on Day 70 after establishment of induced infection. The ivermectin CRC delivers ivermectin at a minimum dose rate of 20 microg/kg/day for 100 days. Infections were induced by daily administration of third-stage larvae for five consecutive days. Nematodes were counted on Day 84, 14 days after treatment of established infection. The treatment with the ivermectin CRC prevented the establishment of Ostertagia leptospicularis, O. ostertagi, Bunostomum trigonocephalum, Cooperia oncophora, C. punctata, C. surnabada, Nematodirus helvetianus, N. roscidus and Strongyloides papillosus by >99% as compared with the untreated controls (p < 0.01). The administration of the ivermectin CRC reduced established adult infections of O. ostertagi, B. trigonocephalum, C. oncophora, C. punctata, C. surnabada, N. roscidus and S. papillosus by >99% (p < 0.01), and reduced established adult infections of O. leptospicularis and N. helvetianus by 96.5 and 98.4% (p < 0.01), respectively.

Abomasum↗
PubMed1997

Anthelmintic treatment strategies: current status and future.

Despite the array of anthelmintics and endectocides and delivery systems available for use in the prevention and control of nematode parasites of ruminants, the number of highly effective control programs that have been developed and even the number of such programs that have been successfully implemented in commercial animal production, there have been no recent innovations or discoveries in regard to strategies, new anthelmintics, or systems for controlling nematode parasites through anthelmintic use. In the traditional sense of chemotherapy-chemoprophylaxis, we have probably achieved the maximum effect of what is possible from excellent anthelmintics developed by the pharmaceutical industry over the last 35 years, i.e. from thiabendazole through levamisole and morantel tartrate, to more advanced benzimidazoles and to the avermectins and milbemycins. At the core of all anthelmintic treatment-related problems is the lingering conception among a large body of animal producers that anthelmintic treatment is the only effort needed to control parasitism and its effects on host animals. This concept has given rise to the long-standing difficulty of drug resistance in sheep nematodes and the not remote possibility of its development in nematodes of cattle. Along with this are serious concerns over environmental toxicity, tissue residues and enormous financial investment to develop new and novel anthelmintic compounds. Progress is being made in current and intensive searches for development and testing of control approaches alternative to anthelmintics, e.g. helminth vaccines, biological control agents such as fungi, selection of resistant sires, alternative chemicals and nematode growth regulators. A timetable for when alternative controls can be developed fully and put into practical use cannot be predicted. It is universally acknowledged among parasitologists that existing anthelmintics must be preserved and utilized judiciously to ensure continued effectiveness. A major example is to be found in strategic or integrated control programs in Australia developed over the last 10 years to combat widespread drug resistance in sheep. Major imperatives for future programs and systems of controlling nematode parasites of ruminants are improved means of getting producers to adopt proven and sustainable methods.

Animal Husbandry↗
PubMed1994

DNA probe-based classification of Simulium damnosum s. l.-borne and human-derived filarial parasites in the onchocerciasis control program area.

The development of polymerase chain reaction-based methods using strain- and species-specific DNA probes for Onchocerca volvulus has permitted classification of individual parasites from every stage of the parasite's life cycle. This technology has been applied on a large scale basis by Onchocerciasis Control Program (OCP) in West Africa. The primary objective of the OCP in using the DNA probes was to obtain accurate estimates of the annual transmission potential of the blinding strain of O. volvulus. The DNA probe classification of larvae collected throughout the OCP area demonstrated that larvae of less pathogenic strains of O. volvulus and other filarial parasites carried by Simulium damnosum s.l. have resulted in a significant overestimation of the annual transmission potential for blinding onchocerciasis. This effect is particularly pronounced along the southern border of the OCP, where the blinding and less pathogenic strains of O. volvulus coexist, and in the north of the control area, where animal parasites, particularly O. ochengi, may even predominate. A second objective of the OCP in applying the DNA probe technology was to determine the distribution of blinding and less pathogenic O. volvulus in infected individuals along the southern border of the control area. Results obtained from these studies have generally confirmed the distribution pattern established by previous epidemiologic studies. In addition, DNA probe classifications have demonstrated that in areas where the blinding and less pathogenic strains of O. volvulus coexist, a single individual may simultaneously be infected with both strains of the parasite.

Africa, Western↗
PubMed1995

[Inquiry of veterinarians in Niedersachsen concerning the occurrence of parasitic diseases and their control in large animals].

In Lower Saxony approximately 3500 veterinarians were asked to fill in a questionnaire focused on the prevalence of parasitic infections in cattle, sheep, pigs, and horses, the preferred control measures and the antiparasitic drugs in use. Although the disappointing low number of only 48 veterinarians that participated in this survey prevented any representative conclusions the following trends were remarkable: gastrointestinal strongyles were the most prevalent parasites in cattle (34.8%), sheep (28.0%), and horses (42.3%). In pigs, ascarids were most often diagnosed (41.9%) followed by the strongyles (27.9%). Horse strongyles were stated as parasites causing problems by 40.0% of the veterinarians. Prophylactic measures are performed by most practitioners alone or in addition to therapy in the case of lungworms or gastrointestinal strongyles. Therapeutic application of anthelmintics is broadly in use against cestodes in horses (65.0%) and liver flukes (cattle: 41.7%, sheep: 33.3%, horse: 57.1%). Benzimidazoles represent the dominating group of anthelmintics in sheep (78.3%), horses (42.1%), and pigs (42.0%). In cattle, ivermectin (27.7%) and benzimidazoles (26.5%) are regularly used. The role of pyrantel is largely restricted to the control of helminths in horses (24.2%) whereas levamisole is stated as a frequently applied drug in cattle (20.5%), pigs (12.0%), and sheep (2.7%). The diagnosis of parasites relies generally on coproscopical examination (93.7%) which is mostly performed by the practitioners themselves (51.1%). In general, the traditional diagnostic tools are regarded as adequate. Approximately 50% of the practitioners declare their interest in a support of veterinary herd management by parasitological institutes.

Animals↗