344 GEORGE IT. F. NUTTALL. 



In other words, infected larvae and nymphs are not infective, whereas the adults are. 

 Infective adults, after having fasted up to seven months, have been placed upon a dog 

 and produced fatal piroplasmosis after an incubation period of about 12 days. 

 Piroplasniosis is the most deadly dog disease if left untreated. Trypanblue, as 

 Nuttall and Hadwen have shown, cures nearly 100 per cent, of the affected animals if 

 they receive an intravenous or subcutaneous injection of 10 cc. of a IJ per cent, aqueous 

 solution of the drug at an early stage of the disease ; it is common for apparently 

 hopeless cases to recover. The chief symptoms of the disease are usually high fever, 

 haemoglobinuria, jaundice, anaemia and a watery condition of the blood. The 

 characteristic parasites, Piroplasma canis, are found in the blood corpuscles, which 

 are largely destroyed, the number of parasitized corpuscles usually mounting steadily 

 until death or recovery takes place. 



Rhipicephalus appendiculatus is fairly widely distributed in Africa. It is a, 

 3-host tick. The female lays 3,000-5,700 eggs which take 32-65 days to hatch at 

 17-19° C. The larvae remain usually 3-7 days upon the host, and, after dropping off,, 

 undergo metamorphosis to nymphs in 4-6 days at 30° C. The nymphs remain 5-11 

 days upon the host and afterwards require 10 days at 37° C. before they emerge as 

 adults. The sexes copulate upon the host, the replete females dropping off after 6-14 

 days if fertilized, after 24 days when unfertilized. Oviposition commences 6-23 days 

 after the female has dropped from the host, the process lasting 15-56 days. The males 

 persist upon the host after the females have left. The sexes occur in about equal 

 numbers. 



The tick remains alive for a long time when unfed, thus larvae and nymphs survived 

 over 333 and 164 days respectively and a single adult has survived over 682 days. 

 The life-cycle, under laboratory conditions, may be completed in 115 days. 



Relation to Disease : R. appendiculatus is the common carrier of Rhodesian Fever 

 or East Coast Fever of cattle, caused by the protozoan blood parasite Theileria parva. 

 The parasite is not transmitted hereditarily in the tick, but only from one stage to 

 another ; thus, if the larvae feed on infected cattle, the nymphs to which they give 

 rise are infective, and similarly, if the nymphs become infected, the adults to which 

 they give rise convey the disease to clean animals. Probably a tick or two suffices 

 to produce infection ; in one experiment conducted in Cambridge, seven adults 

 produced the disease in a calf. 



East Coast fever is ushered in by high fever occurring 10-17 days after the ticks 

 are put on the animal, the characteristic parasites being found in the blood corpuscles 

 5-6 days later. The number of infected corpuscles steadily increases until death, 

 which usually occurs 22-23 days after the ticks are put on. When cattle recover 

 from East Coast fever they are no longer capable of rendering the ticks infective, 

 this being contrary to what is observed in piroplasmosis (see p. 346). 



Rhipicephalus capensis is a 3-host tick. The larvae and nymphs each abandon 

 the host after sucking blood for about 5-8 days. Females remain on the host for 1 1-13 

 days, and begin to oviposit after about 5 days. 



Relation to Disease : According to Lounsbury this tick may convey East Coast 

 fever under experimental conditions. The tick conveys the parasite in a similar 

 manner to /?. apvendicalatus and R. simuSy as described above. 



