TICKS OF THE BELGIAN CONGO. 345 



Rhipicephalus evertsi is a 2-host tick. When placed on the host as a larva it 

 drops off as a gorged nymph after 10-14 days. The adults emerge after 22-25 days, 

 at room temperature. The females remain 6-9 days upon the host. 



Relation to Disease : According to Theiler, R. evertsi conveys equine piroplasmosis 

 in the Transvaal. It remains to be determined which of the two parasites (Pirojplasma 

 caballi, Nuttall, or Nuttallia equi (Laveran) Fran9a) it conveys, since these parasites, 

 which cause similar symptoms, were formerly confused. When the larva + nymph 

 feeds upon an infected animal the adult tick is infective. 



Rhipicephalus sanguineus occurs in many parts of the world in tropical and 

 warm climates, being common upon the dog, but also occurring on other mammals. 

 It is a 3-host tick, its life-history being similar to that of most other ticks in this 

 respect. The female lays 1,400-3,400 eggs, which take 17-19 days to hatch at 30° C. 

 The larvae and nymphs remain usually four days upon the host and take 5-8 and 11-12 

 days respectively to undergo metamorphosis to nymphs and adults. The female 

 stays upon the host 7-21 days before she is replete. Copulation takes place upon the 

 host, the males remaining for an indefinite period after the females have dropped off. 

 The females begin to oviposit 3-6 days after they have fallen to the ground. The males 

 are more numerous than the females. 



This tick shows marked longevity when unfed ; thus under laboratory conditions 

 larvae survived 253 days, nymphs 97 days and adults over 570 days. Under optimum 

 conditions the life-cycle may be completed in 63 days at 30° C. 



Relation to Disease : R. sanguineus has been shown to be the carrier of canine 

 piroplasmosis in India and it doubtless occasionally conveys the disease in Africa 

 and elsewhere. In Africa the chief carrier has been shown to be Haemaphysalis 

 leachi (see p. 343). In the case of R. sanguineus, however, the parasite behaves 

 differently from what it does in H. leachi, for nymphs descended from infected 

 females and adults emerging from nymphs fed upon a dog suffering from 

 piroplasmosis are capable of producing the disease in other dogs upon which they 

 attach themselves (Christophers). 



Rhipicephalus simus, is a 3-host tick, with a life-history similar to that of 

 R. appendiculatus. 



Relation to Disease : R. simus conveys Rhodesian fever to cattle, but it is not the 

 common carrier. The parasites are not hereditarily transmitted in the tick ; it is a 

 case of stage to stage infection, as in R. appendiculatus, which is the usual carrier 

 (see p. 344). In both species the infected ticks cease to be infective after feeding, in 

 other words they " clean themselves." 



Boophilus decoloratus occurs throughout tropical and southern Africa. It is 

 a 1-host tick. When placed upon the host as a larva it rarely drops off until 

 it reaches the adult stage. The females drop off 22-34 days after the larvae 

 have been put on the host, and during this period all stages of development may be 

 observed upon the infested animal. After the larvae gorge they adhere to the host's- 

 skin, undergo metamorphosis in situ, and emerge as lightly chitinized nymphs, which 

 immediately re-attach themselves and in turn proceed to feed to repletion. When 

 (C221) c 



