Increased insensible water loss in feline retrovirus-infected cats

Feline retroviruses such as feline leukemia virus (FeLV) adversely affect the regulation of many vital host systems such as the immune response, erythropoiesis, and nutrient metabolism. In this paper, we describe the disruption of an additional homeostatic mechanism — evaporative water loss — by FeLV. Viremic cats had greater evaporative water losses (24.0 ± 1.4 gm water/kg per day) at low relative humidity levels (19% to 25% relative humidity) when compared to age- and sex-matched control cats (19.7 ± 1.4 gm of water/kg per day [ P < 0.05]). At relative humidity levels greater than 50%, viremic and control cats had similar evaporative water losses. Viremia also resulted in an elevation in the average body temperature (39.1 ± 0.5 °C) compared to control cats (38.4 ± 0.3 °C) ( P < 0.001). However, the energy expenditure of viremic cats (17.14 ± 1.60 kJ/kg/h) was not significantly different from the energy expenditure of control cats (17.02 ± 2.22 kJ/kg/h). The elevated body temperature of viremic cats likely causes a greater increase in evaporative water loss at low relative humidity levels and suggests further study of water balance in retroviral infection is warranted.