FAMILY CHARONACEAE 



1277 



least 2 weeks at 0° C in virulent blood, 

 less than 2 days in hides dried in direct 

 sunlight, 3 days in contaminated wool, as 

 long as 12 days in meat ; is inactivated by 

 glycerine, bile, chloroform, formalin, and 

 2 per cent phenol ; is virulent at least 25 

 days in body of leech, Hirudo boynioni 

 Wharton (HIRUDIDAE), fed on sick 

 animal. 



Literature : Boynton, Philippine Agr. 

 Rev., 10, 1917, 410-433; Daubney, Jour. 

 Comp. Path, and Therap., 41, 1928, 228- 

 248; 263-297; Hornby, ibid., 41, 1928, 17- 

 24; Pfaff, Onderstepoort Jour. Vet. Sci. 

 and Anim. Indust., 11, 1938, 263-330; 15, 

 1940, 175-184; Weston, Jour. Am. Vet. 

 Med. Assoc, 66 (N.S. 19), 1924, 3.37-,350. 



3. Tortor equorum spec. nov. From 

 Latin eqinis, horse. 



Common names : Horse -sickness virus, 

 African horse-sickness virus, virus of 

 pestis equorum, virus of perdesiekte, 

 virus of South African Pferdesterbe. 



Hosts: EQUIDAE—Equus caballus 

 L., horse; perhaps E. asinus L., donkey. 

 Experimentally, also CA N IDAE — Canis 

 familiaris L., dog. CA VI IDAE — Cavia 

 ■porcellus (L.), guinea pig. MURIDAE 

 — Rattus norwegicus (Erxleben) , wild and 

 albino rat ; mouse ; Angora goat ; Mastomys 

 concha, multimammate mouse ; Tatera 

 lobengula, gerbille ; chick embryo (but no 

 virus in hatched chick). Mule and zebra 

 relatively resistant. 



Insusceptible species: HOMI NIDAE 

 — Homo sapiens L., man. LEPORI- 

 DAE- — Oryctolagus cunicnhis (L.), rabbit 

 (no observed disease). 



Geographical distribution : Africa, es- 

 pecially in coastal regions and river 

 valleys. 



Induced disease : In the horse, four 

 types of disease are recognized. Horse- 

 sickness fever, prodromal period 5 to 28 

 days, rise of body temperature to 105° F 

 in 1 to 3 days, with return to normal 

 temperatures in another day or two; 

 sometimes loss of appetite, redness of 

 conjunctiva, labored breathing, and ac- 



celerated pulse ; recovery prompt . Dun- 

 kop or acute pulmonary horse -sickness, 

 prodromal period of 3 to 5 days, severe 

 dyspnea, fever, coughing, frothing at 

 nostrils; fever to 106° F, breathing rate 

 to 60 a minute, nostrils dilated, head and 

 neck extended, ears drooping, sweating, 

 progressive weakness; often fatal. Dik- 

 kop, or cardiac form of horse-sickness, 

 jjrodromal period 5 to 21 days, fever 

 develops slowly, lasts long; edematous 

 swellings of head and neck, symptoms of 

 cardiac dyspnea, sometimes blood spots 

 on conjunctiva, mucous membranes of 

 mouth and tongue bluish, restlessness ; 

 sometimes fatal outcome. Mixed form 

 of horse-sickness, combining features of 

 pulmonary and cardiac types. Horses 

 recovering from natural infections are 

 known as "salted" and possess heightened 

 resistance to the disease. 



Transmission: Not by contact. Mos- 

 quitoes and biting flies have been sus- 

 pected as vectors. Experimentally, bj^ 

 intravenous or subcutaneous injection. 



Serological relationships : Serologically 

 distinguishable strains exist. 



Immunological relationships : Immun- 

 ity to liomologous strain complete after 

 an attack (horse then known as "salted" 

 for that strain), but immunity to hetero- 

 logous strains incomplete. Antibodies 

 absent from young at birth but as high in 

 titer as in dam within 30 hours, presum- 

 ably from colostral milk ; declining gradu- 

 ally over a period of about 6 months. 



Thermal inactivation : At 57.5 to 60° C 

 in 10 minutes. 



Filterability : Passes Berkefeld, Cham- 

 berland F, and Seitz EK filters. 



Other properties : Viable dry at least 

 15 months. Stable in alkaline solutions 

 (to pH 10), unstable in acid (beyond pH 

 6.0). Serum-saline solutions preferable 

 to saline solutions for storage. Particle 

 diameter determined as 40 to 60 milli- 

 microns (mean 50 millimicrons) by filtra- 

 tion methods, 45.4 millimicrons by cen- 

 trifuging. Density 1.25 gm per ml. 

 Isoelectric point at pH 4.8. 



