It is also known as sun stroke or hyperthermia and results in excessive rise of body temperature and absence of sweating.
Etiology: The disease is caused by high environmental temperature and high humidity, may or may not be accompanied with severe muscular activity. The animals with heavy hair coat or kept in poorly ventilated houses are more susceptible. Damage to hypo-thalamus as in FMD, dehydration, poisoning with strychnine, levamisole or claviceps and iodism also result in hyperthermia.
Pathogenesis: When the environmental temperature is high, animal gains more amount of heat from environment. However, due to high humidity, the heat can not be lost in proportional amount through perspiration as a result of which body temperature is elevated. Similarly, due to excessive muscular activity, there is more heat gain and if environment is having high humidity, heat can not be lost which increases body temperature. In such cases, the set point of body temperature in the hypothalamus is not affected.
Clinical signs: There is sudden rise in body temperature, pulse and respiration rates while sweating and salivation are almost absent. The animals become dull and depressed, thirst is increased and they try to lie down in cool places. If the condition persists, animals collapse, show convulsions and die.
Diagnosis: It is diagnosed by clinical symptoms. However, it should be differentiated from hyperpyrexia which is usually related to infectious agents. In cases of septicaemia, growth on blood culture, petechial haemorrhages on mucosae, and changes in blood picture are noticed.
Treatment: If the temperature increases suddenly, cold packs should be applied and animal should be kept at cool places with enough drinking water. These animals should be given enough glucose and protein as supportive treatment to maintain the body requirements. Normal saline should be given intravenously.