zoonoses and communicable diseases common to ... - PAHO/WHO

24 BACTERIOSESThe Disease in Animals: It takes three forms: apoplectic or peracute, acute andsubacute, and chronic. The apoplectic form is seen mostly in cattle, sheep, andgoats, and occurs most frequently at the beginning of an outbreak. The onset is suddenand death ensues rapidly. The animals show signs of cerebral apoplexy and die.The acute and subacute forms are frequent in cattle, horses, and sheep. The symptomatologyconsists of fever, a halt to rumination, excitement followed by depression,respiratory difficulty, uncoordinated movements, convulsions, and death.Bloody discharges from natural orifices as well as edemas in different parts of thebody are sometimes observed.Chronic anthrax occurs mainly in less susceptible species, such as pigs, but is alsoseen in cattle, horses, and dogs. During outbreaks in swine herds, some animals fallvictim to the acute form, but most suffer from chronic anthrax. The main symptomof this form is pharyngeal and lingual edema. Frequently, a foamy, sanguinolent dischargefrom the mouth is observed. The animals die from asphyxiation. Anotherlocalized chronic form in pigs is intestinal anthrax.Anthrax also affects free-roaming wild animals and those in zoos and nationalparks (see section on occurrence in animals).Autopsies of acute cases reveal bloody exudate in the natural orifices.Decomposition is rapid and the carcass becomes bloated with gases. Rigor mortis isincomplete. Hemorrhages are found in the internal organs; splenomegaly is almostalways present (but may not be in some cases), with the pulp being dark red or blackishand having a soft or semifluid consistency; the liver, kidneys, and lymph nodesare congested and enlarged; and the blood is blackish with little clotting tendency.Animals treated early with penicillin recover. Treatment consists of intravenousadministration of 12,000 to 17,000 units/kg of bodyweight of sodium benzylpenicillinfollowed by intramuscular administration of amoxicillin.Source of Infection and Mode of Transmission (Figure 2): Soil is the reservoirfor the infectious agent. The process followed by spores in the earth is a subject ofcontroversy. It has been suggested that there is a cycle of germination and subsequentresporulation, but there is no evidence to this effect. The lifecycle of spores under laboratoryconditions (in culture media) or in sterile soil is extremely long. However,under natural conditions, it seems that their survival is limited to a few years, due tothe activity of saprophytic microbes in the soil. This is probably the case in wild animalreserves in Africa, where attempts to isolate B. anthracis from the soil or waterone or two years after an epizootic yielded negative results, except near the remainsof some animals that died from sporadic cases of anthrax. Turnbull et al. (1991)believe that in order for an enzootic area to be maintained, it would be necessary forthe etiologic agent to multiply in animals. However, a fact to be noted is the long survivalof B. anthracis on the Scottish island of Gruinard, which was abundantly seededwith B. anthracis during the Second World War for purposes of experimentation withbiological weapons. Some 40 years later, viable spores of B. anthracis were stilldetected. It is speculated that this long survival is due to the island’s acidic soil andcold, moist climate, which are unfavorable to the activity of microbial flora.For man, the source of infection is always infected animals, contaminated animalproducts, or environmental contamination by spores from these sources.Cutaneous anthrax is contracted by inoculation during the process of skinning orbutchering an animal or by contact with infected leather, pelts, wool, or fur. Broken