The elimination of the vector Simulium neavei from the Itwara onchocerciasis focus in Uganda by ground larviciding

Garms, R.; Lakwo, Thomson; Ndyomugyenyi, Richard; Kipp, Walter; Rubaale, Tom; Tukesiga, Ephraim; Katamanywa, James; Post, R.J.; Amazigo, Uche

doi:10.1016/j.actatropica.2009.04.001

Cited by 48 publications

(55 citation statements)

References 25 publications

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“…Raybould (1975) suggested the possibility of vector control in the Eastern Usambara focus, pointing out that, because of the long period of larval development of S. woodi near Amani (Raybould and Mhiddin, 1978), control operations would require no more than monthly application of insecticide. Garms et al (2009) found that monthly treatments over approximately 18 months were sufficient to eliminate S. neavei from the various sub-foci in the Itwara focus. Although Walsh and Maegga (1996) considered that the limits of the Eastern Usambara focus needed to be better defined, they also thought that vector elimination was both feasible and desirable in the focus.…”

mentioning

confidence: 99%

“…It is unclear whether S. woodi can maintain the transmission of O. volvulus when its DBR are as low as those recorded in the foci over the last three decades. It is possible that the stable In the Itwara focus in Uganda, S. neavei maintained transmission at DBR of around 20-60 (Garms et al, 2009). Probably because S. neavei is a highly anthropophilic and efficient vector, 4 years of ivermectin distribution in Itwara had little effect on transmission (Garms et al, 2009).…”

mentioning

confidence: 99%

“…It is possible that the stable In the Itwara focus in Uganda, S. neavei maintained transmission at DBR of around 20-60 (Garms et al, 2009). Probably because S. neavei is a highly anthropophilic and efficient vector, 4 years of ivermectin distribution in Itwara had little effect on transmission (Garms et al, 2009). As a consequence, a vector-elimination campaign was initiated and, since September 2003, S. neavei has never been seen in the focus (Garms et al, 2009).…”

mentioning

confidence: 99%

“…Probably because S. neavei is a highly anthropophilic and efficient vector, 4 years of ivermectin distribution in Itwara had little effect on transmission (Garms et al, 2009). As a consequence, a vector-elimination campaign was initiated and, since September 2003, S. neavei has never been seen in the focus (Garms et al, 2009). Members of the S. neavei group are often considered particularly vulnerable to vector elimination because of their limited flight range and restriction to well defined patches of forest (Garms et al, 2009).…”

mentioning

confidence: 99%

“…As a consequence, a vector-elimination campaign was initiated and, since September 2003, S. neavei has never been seen in the focus (Garms et al, 2009). Members of the S. neavei group are often considered particularly vulnerable to vector elimination because of their limited flight range and restriction to well defined patches of forest (Garms et al, 2009). Raybould (1975) suggested the possibility of vector control in the Eastern Usambara focus, pointing out that, because of the long period of larval development of S. woodi near Amani (Raybould and Mhiddin, 1978), control operations would require no more than monthly application of insecticide.…”

mentioning

confidence: 99%

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An apparent halt to the decline ofSimulium woodiin the Usambara foci of onchocerciasis in Tanzania

Kalinga

Post

2011

Annals of Tropical Medicine & Parasitology

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mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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An apparent halt to the decline ofSimulium woodiin the Usambara foci of onchocerciasis in Tanzania

Kalinga

Post

2011

Annals of Tropical Medicine & Parasitology

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Criteria for the differentiation between young and old Onchocerca volvulus filariae

et al. 2009

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Drugs exist that show long-lasting inhibition of embryogenesis and microfilaria production or macrofilaricidal activity against Onchocerca volvulus. Therefore, the patients have to be followed-up for several years. Clinical drug trials have to be performed in areas with ongoing transmission to assess the efficacy on younger worms. In addition, future vaccine trials may also require demonstrating efficacy against establishment of new worms. For the evaluation of the efficacy, it is necessary to differentiate between older worms, which were exposed to the drug, and younger worms newly acquired after drug treatment or vaccination. Here, we describe criteria for the differentiation between young and old filariae based on histological studies of worms with a known age from travellers, or from children, or patients living in areas with interrupted transmission in Burkina Faso, Ghana or Uganda. Older worms were larger and presented degenerated tissues. Gomori's iron stain showed that the worms accumulated more iron with increasing age, first in the gut and later in other organs. Using an antibody against O. volvulus lysosomal aspartic protease, the gut of young worms was stained only weakly; whereas, it was stronger labelled in older worms, accompanied by additional staining of hypodermis and epithelia. Using morphological and immunohistological criteria, it was possible to differentiate young (1–3 years old) from older females and to identify young males.

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Assessments of the transmission of Onchocerca volvulus by Simulium sanctipauli in the Upper Denkyira District, Ghana, and the intermittent disappearance of the vector

et al. 2015

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Following studies on the transmission of Onchocerca volvulus (Leuckart) by Simulium sanctipauli Vajime & Dunbar (Diptera, Simuliidae) in Upper Denkyira District in Ghana in 2001 and 2002 (Kutin et al., Med Vet Ent 18:167-173, 2004), further assessments were carried out in 2006 and 2013/2014 to determine whether transmission parameters had changed since community-directed ivermectin treatment (CDTI) began in 1999. There were no marked changes of the transmission intensities in 2006. Only slight, but non-significant, reductions were observed in infection rates of parous flies with larval stages (L1-L3) of O. volvulus from 44.1 % (of 1672 parous flies) in 2001/2002 to 42.1 % (506) in 2006 and from 6.5 to 5.9 % of flies carrying infective larvae in their heads. This suggested that there was an ongoing transmission in the area and the parasite reservoir in the human population was still high. Unexpectedly, further assessments conducted in October 2013 and March and October 2014 revealed that the vector S. sanctipauli had apparently disappeared and transmission had ceased, probably as a result of intensified gold mining activities along the rivers Ofin and Pra. The water of both rivers was extremely turbid, heavily loaded with suspended solids, probably preventing the development of blackfly larvae. Some breeding and biting of Simulium yahense Vajime & Dunbar was observed in a small tributary of the Pra, the Okumayemfuo, which is not affected by gold mining. However, the infection rate of flies was low, only 3.7 % of 163 parous flies were infected with first stage (L1) larvae of O. volvulus.

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The elimination of the vector Simulium neavei from the Itwara onchocerciasis focus in Uganda by ground larviciding

Cited by 48 publications

References 25 publications

An apparent halt to the decline ofSimulium woodiin the Usambara foci of onchocerciasis in Tanzania

An apparent halt to the decline ofSimulium woodiin the Usambara foci of onchocerciasis in Tanzania

Criteria for the differentiation between young and old Onchocerca volvulus filariae

Assessments of the transmission of Onchocerca volvulus by Simulium sanctipauli in the Upper Denkyira District, Ghana, and the intermittent disappearance of the vector

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