Modelling the economics of animal health control programs using dynamic programming

A new application of an optimization tool, dynamic programming (DP), is described to model the economics of animal health control programs. To demonstrate the value of this technique, a model is applied to determine optimal net benefits of controlling East Coast fever (ECF) in Malawi Zebu cattle in the Lilongwe plateau. The objective function was the present value of net benefits due to treatment, defined as mortality savings minus treatment costs. Mortality savings were based on decreased mortality from ECF following treatment. Model constraints included herd size, animal (herd) nutritional requirements, and program budget. Treatment options were tank dipping in acaricide, and vaccination. Secondary data from a dipping trial of 1800 Malawi Zebu cattle conducted from 1991 to 1994 were used to determine probabilities of mortality. Total optimal net benefits of long-term treatment (25 years, i = 10%) from vaccination (Malawi Kwacha (MK) 21 069) exceeded benefits for treatment with chlorfenvinphos acaricide (MK15 203).