Our study indicates that there is a large burden of skin disease in children in Fiji. Over one quarter of school aged children in our cross-sectional study had active impetigo at any given time and almost half of impetigo-free children in our prospective cohort study experienced a new episode of active impetigo during the ten month study period. Nearly one-third of scabies-free children in the cohort experienced a new episode of scabies during the study period. Impetigo and scabies were also highly prevalent diseases in the infants observed in our study, although less common than in children. The majority of cases of active impetigo in the children in our study were caused by GAS (79.8% in school aged children, and 49% in infants), although S. aureus was also a common cause (57.4% in school aged children and 69% in infants).
A recent review of the prevalence of childhood skin diseases in developing tropical and subtropical countries concluded that the prevalence of impetigo is commonly in the range of 5–10% and the prevalence of scabies is in the range of 1–2% 
. Many of the studies included in this review were from sub-Saharan Africa. Studies from the Pacific, including ours, suggest that the prevalence of impetigo and scabies is significantly higher in the Pacific region 
. The reason for this is not clear. A significant finding in our study was the higher risk of GAS impetigo and scabies in Indigenous Fijian children.
We have previously noted higher rates of GAS disease in Indigenous Fijians, including invasive GAS disease and rheumatic heart disease 
. Other investigators have noted higher rates of other Gram-positive infections, including radiographically proven pneumonia 
We used a simple method to calculate incidence density and found a very high incidence density of new cases active impetigo and scabies. It is likely that our figures are in fact an underestimate of the true incidence for three reasons. First, we may have missed new cases of impetigo and scabies that erupted and then healed in between the two-monthly study visits. A study in Mali estimated that 41% and 53% of cases of impetigo and scabies lasted for less than one month respectively 
. Second, we required a child to be disease-free at the previous visit before a case could be counted as a new case; we therefore did not count new lesions in children with existing lesions as incident cases – to detect these cases would require more intensive surveillance techniques such as interval photography. Third, the method of clinical examination in this study may have underestimated prevalence because the entire body was not always examined. There were also other limitations to our study including potential sources of bias. There was the potential for participation bias because of differing enrolment rates between schools and between studies, and there was also the potential for inter-rater variability and bias because of multiple observers, although we attempted to standardize the clinical examination methodology as much as possible.
Impetigo and scabies have been considered public health problems in developing countries for decades 
, however there has been little progress in their control on a global scale 
. It is estimated that there are more than 111 million prevalent cases of GAS pyoderma globally 
. Although often considered as a benign disease, impetigo can lead to more serious illnesses including cellulitis and abscess via local spread, bacteremia and sepsis following haematogenous invasion, as well as the non-suppurative sequelae of acute post-streptococcal glomerulonephritis and possibly acute rheumatic fever 
. The highest incidence rates of invasive GAS disease have been described in tropical developing countries and impetigo has been identified as an important portal of entry 
. The mortality rate from invasive GAS disease in these settings is high; in Fiji the all-ages case fatality rate is over 25% 
. Post-streptococcal glomerulonephritis in tropical regions almost always follows impetigo GAS infection rather than GAS pharyngitis as it does in industrialised countries 
. There is evidence to suggest that acute post-streptococcal glomerulonephritis may contribute to chronic renal impairment in adult life 
. Scabies on its own can cause significant clinical impact, most notably sleep disturbance that occurs in up to 70% of cases 
. In addition to their clinical impact, impetigo and scabies also cause a considerable financial burden to individuals, families and health services. From the limited published data, impetigo and scabies account for between 12.3% and 23.7% of primary health care centre presentations in tropical countries, placing a significant drain on these services 
. Impetigo and scabies leads to absence from school and costly treatment. In a study in Mexico, the average period of absence from school for scabies was 8 days and for pyoderma 15 days, and the average cost of treatment for scabies and impetigo was US$24 and US$52 respectively 
Given the clinical and economic burden of impetigo and scabies, and the sheer volume of cases in tropical developing countries, there have been renewed appeals for an organized global effort to control these diseases 
. However, in many countries where impetigo and scabies are common, there are competing health problems that carry higher morbidity and mortality. Therefore, it has been suggested that control measures be simple, practical, of low cost and commensurate with the level of the priority of the problem in the local context 
. We have recently validated an algorithm for the identification and treatment of common childhood skin conditions that can be incorporated into existing Integrated Management of Childhood Illness programs 
. This algorithm is designed to improve case management of childhood skin diseases at the primary health care level, with minimal need for additional infrastructure and training.
In countries such as Fiji that have been able to significantly reduce high mortality diseases and in which skin disease is common, it may be appropriate to consider initiatives aimed at controlling impetigo and scabies on a broader public health level. Whilst mass drug treatment with scabicides can produce short-term reduction in scabies disease burden 
, most experts believe that a sustained reduction requires an integrated approach that includes the following elements: public health education, improved case management, improved drug supply and potentially improvements in personal hygiene practices 
. Intervention studies in the Pacific region aimed solely at scabies control have been shown to achieve their aim of controlling scabies with a flow-on effect on scabies-associated impetigo, but they have had less effect on non-scabies impetigo 
. The finding of a large burden of impetigo independent of scabies in school-aged children in our study suggests that the case may be the same in Fiji 
. Further research into practicable, effective and sustainable control measures is required.
A GAS vaccine could also be an important advance in primary prevention of impetigo. However, major questions remain about a GAS vaccine designed to prevent skin disease. First, little is known about the mechanism of immunoprotection against impetigo 
, because group A streptococcal vaccine research has largely focused on protection against pharyngitis and invasive disease. Second, it is not clear what effect a GAS vaccine would have on S. aureus
in impetigo lesions. As we have shown, S. aureus
is a common infecting agent in impetigo, and S. aureus
and GAS can co-exist in individual lesions. It is possible that circulating GAS strains removed by a vaccine would only be replaced by S. aureus
strains that are currently the victims of competitive inhibition by GAS. Third, the design of a GAS vaccine against skin disease would need to be specifically tailored to cover common types of GAS that cause impetigo.
Our study confirms that impetigo and scabies are endemic diseases in Fiji causing a substantial disease burden, consistent with findings from around the region. These findings, coupled with the potential for clinical complications and a heavy socio-economic impact, suggest that it is time for more concerted action against these diseases in Fiji and other tropical developing nations.