A decrease in the number of STH and scabies cases diagnosed by health centre staff from 50 health facilities in Unguja and Pemba after the LF elimination programme had distributed ivermectin and albendazole between 2000–2005 was found in all age groups. We report these results conscious that the methodology we employed has limitations. However, we also consider that the method merits further investigation as MDA programmes upscale towards the milestones set by WHO with regards to achieving the maximum coverage of preventive chemotherapy by MDA for onchocerciasis, lymphatic filariasis, schistosomiasis and soil transmitted helminths (http://www.who.int/neglected_diseases/resources/en/index.html). Specifically, it is envisaged that over one billion annual treatments are required if targets for control or elimination of these diseases are to be met.
The limitations that can be identified reflect the settings of a busy health centre environment, where diagnosis is made predominantly on history and symptomatology. In the case of helminth infections, only severe or moderate cases which give rise to symptoms will present, whilst the presentation of those with low grade infection is less likely. Diagnosis of scabies is more reliable due to characteristic skin lesions presented. Despite such differences in infection status and reliability of diagnostic methods used in health centres, the trends we describe for both STH and scabies after prolonged ivermectin and albendazole distribution within the community are similar. Given the unspecific nature of clinical presentations of STH, consistency in recording STH in health centre records is important. Health staff diagnose on the basis of experience, however, as the same staff tend to be in post over many years we would argue that the data obtained can be attributed to consistency in diagnoses and prescribing. Whilst low grade and hence less intense infections would not present to clinics yet still benefit from the anthelminthic benefits of MDA, the results can be interpreted as a consistent decline in the numbers of people with moderate to severe symptoms associated with STH. Despite these limitations we believe the consistent decline in two groups of infections determined using this rapid methodology allows retrospective analysis of data. This would not be possible using classical approaches. The trends of decline were observed in two different islands, in all age groups and in 50 health centres for conditions which are biologically different in terms of transmission yet are affected by the drugs deployed in MDA, supporting the further exploration of the methodology in a more controlled setting. Importantly, the trends in scabies can be viewed as a control for the STH observations as scabies is more easily diagnosed by health staff and the scabies results mirror those of STH in both the districts and the islands. We did not record the total number of individuals who presented at these clinics during the study period.
The results are also consistent with the reported high MDA coverage  during the period of 2000–2005. The Global LF programme and onchocerciasis programmes are together administering MDA in around 60 countries, and over 600 million people each year are benefitting from these drugs, which have broad anthelminthic impact [3, 8]. There is therefore a need to evaluate the broader synergistic impact on both STH and scabies of MDAs and the approach we describe merits consideration for the reasons we articulate below.
We suggest that the use of the gold standard approach the Kato-Katz test, as well as other more sensitive concentration techniques, would be both impractical and costly to undertake at scale as they require extensive stool collection and laboratory diagnosis. Furthermore they cannot be carried out retrospectively. Indeed, despite the extensive distribution of anthelminthics as part of LF and onchocerciasis programmes, we are not aware of any pre-MDA STH or scabies baseline data being available. While it may be appropriate to evaluate the outcomes using classical methods in limited settings, to contemplate, the use of such methods at scale when there will have been a significant reduction in the sensitivity of the test because of wide scale MDA would seem inappropriate.
National guidelines stipulate that only children of 5 years old (90 cm in height as a surrogate) and above should receive the medication for lymphatic filariasis, hence the youngest age group (birth-5 years) would not be treated. However, an observed decline in STH and scabies for this group after the initiation of MDA suggested that the treatment of the older age groups impacted on the birth-5 year old group also. This may also have been attributed to the national helminth programme, which targeted the younger age groups during the same period  although this confounder would not be present in the older age groups nor would influence the scabies results.
STH has been recognised as a problem in Zanzibar since surveys revealed prevalence in school aged children to be 72% for Ascaris lumbricoides, 94% for Trichuris trichiura and 95% for hookworm in Pemba . This study indicated a marked decrease in reported STH diagnosis, with this reduction likely to be in those with moderate or severe infections of hookworm and Ascaris. Studies in Haiti and Sri Lanka indicated that significant decreases in STH were observed [14, 15] following the filariasis control programme, emphasising the effectiveness of albendazole treatment.
In our study the total number of scabies cases identified was considerably lower than during the period prior to the initiation of MDA for LF. Studies by Bockarie et al.  showed the effectiveness of ivermectin on scabies, particularly in areas of high prevalence, where a disappearance of scabies due to the impact of ivermectin was demonstrated . Scabies is diagnosed at the primary health care level when patients present with itchy papules and characteristic rash , although definitive techniques including dermoscopy, skin scraping and the adhesive tape test give a precise diagnosis . Although mass screening and treatment of individuals affected by scabies would lead to a significant decrease in scabies prevalence, Gilmore  identified that it would it be difficult to sustain the implementation of such protocols over extended periods. Ivermectin is not an indicated drug for scabies despite its efficacy [7, 10] and the benefits of ivermectin for scabies can only be assessed where it is used in LF and onchocerciasis programmes.
Speich et al.  estimated the cost of a Kato-Katz test as 1.73 US$ on Zanzibar, a figure which contrasts with the annual costs of LF MDA distribution in Tanzania of 0.26-0.54 US$ per person . We consider that it is not feasible to initiate large scale stool examination using techniques which are costly, time consuming and insensitive for the assessment of the impact of MDA for LF and onchocerciasis. The approach we suggest, which despite its limitations, appears to provide consistent results, could be applied retrospectively and does not require the deployment of technical staff or the collection, transport and storage of stool samples.