Diseases of Domestic Animals in Nyasaland. 



23 



Disease set up in Various Animals by T. pecorum, Nyasaland — The Wild 



G. morsitans Strain. 



Cattle. — Only one ox was experimented with. It was sent into the 

 " fly-country," and as a result incurred a double infection of T. pecorum and 

 T. caprce, and died in 140 days. 



Goats. — The wild flies brought up from the " low-country " were fed, as a 

 rule, on a goat, monkey, and dog. As the flies were often infected with 

 several species of pathogenic trypanosomes, the result was many cases of 

 mixed infection. In 50 experiments with goats, 10, or one-fifth only, were 

 infections with T. pecorum alone. As T. pecorum is the most rapidly fatal 

 trypanosome to goats among the various kinds of trypanosomes found in this 

 locality, it may be assumed that the 28 goats which died of mixed infection 

 owed this mainly to the T. pecorum infection. 



Pig. — In eight feeding experiments with wild G. morsitans, only two showed 

 a pure infection with T. pecorum. One died in 21 days and the other is still 

 alive after 16 days. Another pig was inoculated from Dog 1702 and is still 

 alive after 21 days. This species of domestic animal may, therefore, be said 

 to be susceptible to this disease. 



Monkey. — To this strain as to the "Wild-game strain the monkey shows its 

 refractoriness. These animals had the same chance of taking the disease as 

 the goats and the dogs, but in 28 experiments the monkeys only became 

 infected six times (21*4 per cent.), whereas in 50 goats there were 42 infections 

 (84 per cent.), and in 41 dogs 35 (85 - 4 per cent.). The duration of the disease 

 in the monkey is also long, the average in four cases being 138 days. 



Dogs. — The Wild G. morsitans strain is fatal to dogs, killing them, on an 

 average, in 41 days. In 35 cases of this disease among dogs, only five have 

 survived to the present date. One of these may be said to have recovered, 

 as the trypanosomes disappeared from the blood and the blood ceased to be 

 infective. The other four still show trypanosomes in the blood after 258, 231, 

 210, and 78 days respectively. The dog may, therefore, be said to be as 

 susceptible to the Wild G. morsitans strain of T. pecorum as the goat, few 

 escaping the disease when bitten by an infective fly. 



Guinea-pigs and White Hats. — The susceptibility of these animals to the 

 Wild G. morsitans strain would be considered by some to go to prove that 

 exaltation of virulence obtains after passage through the fly. This, however, 

 is doubtful. Passage through the fly would more probably restore the 

 trypanosome to its normal form — sometimes increasing, sometimes decreasing, 

 its virulence for a particular animal. 



