A mouse lethal dose assay for detection and titration of Cowdria ruminantium (Kwanyanga strain) in goats and ticks.
Endris RG, Haslett TM, Birnie EF, Hess WR.
USDA-ARS, Plum Island Animal Disease Center, Greenport, NY 11944.
A mouse lethal dose assay was used to detect a mouse pathogenic strain (Kwanyanga) of Cowdria ruminantium, the etiological agent of heartwater in goats and ticks. The titer of the rickettsial organisms in goat blood was directly related to the febrile response of the goat and the rickettsia were undetectable after the fever subsided. The maximum rickettsial titer in goat blood was 10(3) mouse LD50 ml-1. Cowdria-infected goat blood was shown to retain infectivity when held on ice for up to 2 h, but when held at room temperature infectivity declined by greater than 50% in 2 h. The mouse assay detected Cowdria in feeding female Amblyomma variegatum only on the eighth day of feeding and in feeding males on the second and eleventh days of feeding. Cowdria was shown to persist in the hemolymph of the soft tick Ornithodoros coriaceus for a period of at least 2 years.
PMID: 2705290 [PubMed - indexed for MEDLINE]
African swine fever virus infection in the Iberian soft tick, Ornithodoros (Pavlovskyella) marocanus (Acari: Argasidae).
Endris RG, Hess WR, Caiado JM.
Plum Island Animal Disease Center, USDA-ARS-NAA, Greenport, New York 11944-0848.
One thousand six hundred Ornithodoros (Pavlovskyella) marocanus Velu larvae were fed on a pig infected with African swine fever virus (titer: 10(7.4) HAd50/ml), and 1,600 larvae were fed on an uninfected pig. Ticks in each group were compared for mortality rates, mean time to death for ticks that died, mean time from feeding to either molting or eclosion, percentage of ticks that eclosed or molted, and the number of blood meals per nymph or instar. Cumulative virus-induced mortality for all immature stages (larvae to adult) of O. marocanus that had been fed as larvae on a pig infected with African swine fever was ca. 73% over a 390-d period. In contrast, less than 9% mortality was observed among ticks fed on uninfected pigs. Mean time to death for infected ticks was 15-87 d versus 10-17 d for uninfected ticks. Differences in the premolt period (number of days from blood meal to molt) between infected and control ticks were not observed. Mean premolt periods for larvae and first-, second-, third-, fourth-, and fifth-instar nymphs fed on pigs were 7, 9, 15, 11, 15, and 15 d, respectively. The majority of infected and all uninfected ticks required only one blood meal from pigs to molt. Mean weights for unfed second-, third-, and fourth-instar nymphs and males and females were 0.50, 0.67, 3.07, 3.63, and 5.91 mg, respectively.
PMID: 1404269 [PubMed - indexed for MEDLINE]
Waarbij we ons misschien af zouden moeten vragen: wat was het doel van deze studies?
a) kijken of de teek een vector is van een betreffend pathogeen;
b) kijken tot in hoe verre de teek een geschikte vector is voor een betreffend pathogeen!