Ii\P"LL'KNfK OK CLIMATE ON ANIMAL I)[S1:A.SI-:. 4// 



1. Bacterial diseases. 



2. Tick or insect-borne diseases. 



3. Diseases caused by belminthic ])arasites. 



4. Diseases due to toxic plants. 



Of tbe tirst .c^roup it is not intended to say ver\ much, and 

 space only permits of one example of this type being dealt with. 

 This example, h.owever. has a general interest, and is met with 

 in the disease anthrax. 



In anthrax we have an example of a bacterial disease of 

 jiractically world-wide distribution, and to which all of the 

 domesticated and many non-domesticated animals are susceptible. 

 The organism rcsponsil)le for the disease is a bacillus known 

 as the Bacillus anthracis. a facultative parasite of aerobic habits. 



It is known that the disease can be contracted through the 

 channels of inoculation and inhalation, but the commonest route 

 of infection in the lower animaU is ap])arcntly ingestion. In- 

 fection through this channel follows the ingestion by the animal 

 of either food or water con.taining the organism, or more par- 

 ticularly its spores. The importance of foods grown on infected 

 areas or special foodstuti's ])re])are(l from contaminated material 

 serving as vehicles of infection is recognised in this connection, 

 l)Ut the part played by infected j-astures acting as sources of 

 infection to the animals grazmg over them is the aspect which 

 is of most importance for oin^ present consideration. 



In many parts of the world the tlisease is regarded as being- 

 associated with certain, localities, and these frequently resemble 

 each other in Iteing places situated in the neighbourhood of water 

 or in tlie soil being of a moist or damp character. Instances 

 of stich localities are marshes, swamps, near natural water pools, 

 along river banks, and on plains which are periodically flooded, 

 such as recognised flood-plains, and river deltas. These are 

 widely-recognised facts, but in order to explain them and also 

 other observations made later on, it is necessary that we should 

 learn something of the ])iology of the bacillus causing the disease, 

 and hence we may pause here in order to do tliis. 



A great deal is known about the biology of this bacillus, 

 but we will only deal with the points of greatest importance to 

 us. The Bacillus anthracis is an oganism which is a facultative 

 ])arasite — that is to say, it is an organism capable of existing 

 or leading a saprophytic existence outside the animal body, two 

 of its common habitats under these conditions being soil or 

 water. In cultivation it is an organism reciuiring free oxygen 

 for its development, hence it is referred to as bemg aerobic in 

 character, and it is also known that the bacillus which represents 

 the multiplicative phase of the organism is capable of multiply- 

 ing at temperatures between 12" C. and 45° C, the optimum 

 temperature being about, 32° C. to 35'' C. The bacillus itself 

 is not very resistant to adverse circumstances, behaving as most 

 ordinary bacteria do under these conditions It is soon destroyed 



