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Abstract This study aims to develop a tool that calculates the optimal preventive maintenance interval when the income from the operation of an asset changes. The income can be modified by market disturbances or by the decrease in the efficiency of the asset due to its degradation. A system with four states is designed to model the operation and maintenance process: operational, corrective, preventive, and degraded operation is mathematically modeled. The system evolves over time, according to a semi-Markovian process. The transitions and sojourn times between each state produce the accumulation of costs and income as returns (negative or positive) in a variable called average accumulated return. The average accumulated return is defined by a system of difference equations that are solved by applying the z-transform. The solution is a function that is dependent on the preventive interval. By derivation, the mathematical expression of the optimal preventive interval that maximizes the average accumulated return is obtained. From this expression, it can be deduced that the size of the optimal preventive interval is directly affected by the income from the asset operation. Higher income increases the size and lower income decreases it. For this reason, the maintenance manager must observe the changesoccuring in the income from the use of his equipment in order to optimize his management economically.

Introduction: Herpesvirus infections have been highlighted as emerging diseases affecting wildlife health and the conservation of several taxa. Malignant catarrhal fever (MCF) and infectious keratoconjunctivitis (IKC) are two viruses that infect wild ruminants. Nevertheless, epidemiological data on herpesviruses in South American wild ruminants are limited. An outbreak of caprine gammaherpesvirus-2 (CpHV-2) that recently was suspected as the cause of MCF in southern pudus (Pudu puda) prompted the need to conduct molecular screenings in Chilean cervids to understand the epidemiology of herpesviruses. The aim of this study was to determine the occurrence and genetic diversity of herpesviruses in free-ranging cervids from Chile. Methods: Herpesvirus infection was assessed in antemortem blood samples (n = 86) from pudus (n = 81) and huemuls (Hippocamelus bisulcus) (n = 5), as well as postmortem samples of spleen (n = 24) and lung (n = 3) from pudus, using a nested pan-herpesvirus PCR assay. Results: Combining all suitable sample types, DNA of pudu gammaherpesvirus-1 was detected in five pudues and five huemuls, with an overall prevalence of 9.90% (n = 10/101; 95% CI = 5.11-17.87%). One pudu tested positive for ovine gammaherpesvirus-2 (n = 1/96; 1.04%; 95% CI = 0.05-6.49%), and one pudu tested positive for a Macavirus sequence with 98.63 similarity to ovine gammaherpesvirus-2 (n = 96; 1.04%; 95% CI = 0.05-6.49%). Discussion: To the best of our knowledge, this is the first report of a herpesvirus in huemul and of ovine gammaherpesvirus-2 in Chile. Our results also confirm the active circulation of herpesvirus in free-ranging cervids in Chilean Patagonia, and as such, MCF should be considered as a possible cause of disease in free-ranging Chilean pudus and livestock species. Further research is necessary to develop a plan of systematicmonitoring (serological and pathological screening) of herpesviruses in Chilean wild and domestic ruminants to understand their diversity and impact on animal health and conservation. [ABSTRACT FROM AUTHOR]