  Despite a low global prevalence, infections with Sarcoptes scabiei, or
scabies, are still common in remote communities such as in northern Australia
and the Solomon Islands. Mass drug administration (MDA) has been utilised in
these communities, and although prevalence drops substantially initially, these
reductions have not been sustained. We develop a compartmental model of scabies
infection dynamics and incorporate both ovicidal and non-ovicidal treatment
regimes. By including the dynamics of mass drug administration, we are able to
reproduce the phenomena of an initial reduction in prevalence, followed by the
recrudescence of infection levels in the population. We show that even under a
`perfect' two-round MDA, eradication of scabies under a non-ovicidal treatment
scheme is almost impossible. We then go on to consider how the probability of
elimination varies with the number of treatment rounds delivered in an MDA. We
find that even with infeasibly large numbers of treatment rounds, elimination
remains challenging.
