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The ovicidal value of concentrated vapors of chloroform, sul. furous acid, ammonium sulfide, ethel dixanthogen, BHC, formalin, and phenol has been reported (Enigk and Grittner 1953).
A report of the resistance of 0. moubata to various sheep dips (Blacklock 1912) is of little contemporary interest.
Disinfection of Personal Effects
Blankets, bedding, and clothing may be disinfected by exposure in a tight container to a temperature of 82°C. for half an hour (Hopkins and Chorley 1940).
In a carefully conducted experiment, Garnham (1926) found, contrary to certain textbook statements, that burning of African huts infested with 0. moubata is an effective means of killing these ticks. He suggested pulling down the straw roofing and piling it inside mud hut walls for burning. This may be the only means of control where the indigenous population does not work for pecuniary gain, Otherwise burning is uneconomical un less the situation is serious. More permanent housing, in which infestation may be controlled or better still prevented, should be substituted whenever possible. Burning infested buildings has long been the indicated control method in many parts of Africa. Flame throwers are sometimes used to good effect where ticks are lodged in shallow cracks in buildings that withstand fire, Jack (1931) obtained control against tampans in nine-inch walls of pigsties by burning brushwood on both sides of them. Burning against only one side and spraying with a ten percent emulsion of paraffin (i.e. kerosene) had failed.
A reward of sixpence for every twenty ticks collected on a South African farm yielded 73,000 ticks one year and over half a million in several years. Laborers placed a thin layer of drift manure along the inside walls of their huts and there collected the ticks as they came to hide. Small holes dug inside and out side the doors and filled with drift manure were also found to be favorite hiding places (Annecke and Quin 1952).
0. moubata is the only known tick vector of African tick-borne relapsing fever (Borrelia duttonii) of East, Central, and South Africa. A few cases of this disease have been reported from Eque toria Province in the Sudan. No evidence supports certain pub. lished maps showing known extensive distribution of tick-borne relapsing fever in many areas of the Sudan. It should be noted that populations of this tick from burrows of wild animals have not been found infested with spirochetes.
It is claimed that some specimens naturally infected with rickettsia, Coxiella burnetii, the causative organism of Q fever, have been found in Ruanda Urundi, and that in Kivu others have been taken infected with an organism referred to as "Bashi virus rickettsia”.
The etiologic agent of food poisoning, Salmonella enteritidis, has been recovered from this tick in Africa.
0. moubata has not actually been found infected in nature with the pathogeni organisms of any other human disease, but experi. mental data strongly indicate further research in this respect.
Tampan bites may cause considerable irritation. Circumstan tial evidence suggests that persons long victimized by bites of this tick may develop an immunity to them.
0. moubata is an experimental vector of fowl spirochetosis (Borrelia anserina). It is of negligible importance in transmission of Salmonella bacteria and of Aegyptianella pullorum (a protozoan). The bacterium that causes avian cholera (Pasteurella avicida) survives only a few days in 0. moubata.
Experimental Disease Relations
Viruses and Rickettsiae
The use of 0. moubata and other Ornithodoros species for trans. porting a mmber of pathogenic organisms for experimental purposes has been suggested.
This species is easily infected with Q fever (Coxiella burnetii) and is capable of transmitting the organism by its bite. A diagnos tic test for a fever, using 0. moubata for feeding on a suspected host, has been developed.
Rickettsia prowazekii, the causative organism of classical typhus, and R. typhi, that of mirine typhus, develop in 0. moubata. The former rickettsia can be transmitted transovarially and the latter can be found in eggs and coxal fluid of infected ticks. No multiplication of R. tsutsugamushi, the causative organism of scrub typhus, occurs in 0. moubata; the tick is therefore not a likely vector of this unusually host-specific rickettsia.
O. moubata maintains infection with the virus of Russian spring summer (Far Eastern) encephalitis. It has also been shown that these ticks can be infected with western equine encephalitis virus. The virus causing murine poliomyelitis (strain Columbia SK) is destroyed or inactivated in blood ingested by the tampan, Yellow fever is not transmissible by this tick. A Congo ricket to sia of the boutonneuse fever type (boutonneux-pourpre) remains virulent in ticks fed on infected guinea pigs for two months but not for six months.
Tularemia (Bacterium tularense) is transmitted by the bite of 0. moubata and is also transovarially transmitted to progeny. Bacillus anthracis, the causative organism of anthrax, is not transmissible and apparently kills the ticks, although it does remain virulent in the tick's body long after death, The etiologic agent of food poisoning, Salmonella enteritidis, has been recovered from this tick in Africa.
Spirochetes of Relapsing Fever
0. moubata is capable of harboring and transmitting other Borrelia species besides B. duttonii. This is of considerable interest since in other parts of the world many species of Borrelia are host-specific and tick hosts are spirochete specific.
Spirochetes Other Than Relapsing Fever Weil's disease (Leptospira icterohaemorrhagiae) survives for about forty days in living 0. moubata, remains virulent in the body long after the tick's death, and can be transmitted when infected ticks bite.
Filariae may develop in the body cavity of 0. moubata but transmission appears to be unlikely.
Virulent trypanosomes may remain in the tick's gut for as long as five years, but transmission is apparently impossible and transovarial infection does not occur.
It appears that Toxoplasma gondii cannot be transmitted by 0. moubata although the organism survives in the tick for almost Ewo weeks after artificial inoculation.
The suggestion has been made that tick bites, such as those of 0. moubata, may be initially responsible for tropical ulcer.
0. moubata might be confused only with 0. savignyi in the African fauna. However, since 2, moubata lacks eyes, which in 0. savignyi are present as two pairs of small, round, equal sized,
shiny black spots in the lateral groove, one pair above coxa I and one pair between coxae III and IV, there should be no real difficulty in distinguishing the species. Tarsal differences mentioned in Nuttall et al (1908) are too variable for application. Adults average about 8.0 mm. long by 6.0 mm. or 7.0 mm. wide, although freshly engorged females may reach 11.0 mm. in length. 0. savignyi is usually somewhat larger, averaging about 11.0 mm. Iong. The mammillated integument, conspicuous tarsal dorsal protuberances, and absence of cheeks easily distinguish both 0. moubata and 0. savignyi from all other African species. Males are often a little smaller than females and their genital aperture is a short, rounded opening as compared with the broad slit of the female. Nymphs have no genital aperture, but in larger instars a small round depression is present in its place.
In a study of the sexual differences in this species, Nuttall (in Cunliffe 1921) has shown that the average male is smaller than the average female, though extremes overlap, and that the same is true for the size of the genital aperture of the two sexes.
An estimate of the stage of development of immature stages can be made on the basis of differences in mouthparts, legs, and spiracles (Cunliffe 1921).