ABSTRACT
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.
Subject(s)
African Swine Fever , Insect Viruses , Ticks/microbiology , Animals , Female , Male , Swine , Ticks/physiologyABSTRACT
The establishment of epidemiological studies of African swine fever involves the collection of large numbers of the soft tick, Ornithodoros erraticus, to assess the maintenance and spread of the disease in the semi-arid southern areas of Portugal. An on-farm monitoring system involving solid carbon dioxide trapping of ticks was used. This capture method proved to be both simple and effective when compared with manual collection. Both adult and stadial ticks were attracted by the traps making this method suitable for epidemiological surveillance studies of any disease which involves the Ornithodoros as a vector.
ABSTRACT
Three laboratory colonies of the argasid tick Onithodoros moubata porcinus van der Merwe were started from collections made in 1983 at three different sites in Zimbabwe. All of the colonies contained ticks infected with African swine fever (ASF) virus that was readily transmitted by bite to domestic pigs. Although they were maintained on virus-free pig blood, ASF virus infections persisted in the colonies for at least 1 yr. Despite the fact that ASF virus passes transstadially, sexually, and transovarially in this tick species sometime during the following year, the virus disappeared from the colonies. Studies comparing fecundity in infected and uninfected lots of O. moubata porcinus showed that mortality rates were considerably higher among the infected ticks. A similar study with Ornithodoros erraticus Lucas, a tick that harbors and transmits ASF virus on the Iberian Peninsula, gave essentially the same results. This is probably a factor involved in the clearance of ASF virus from tick populations that are not subjected to reinfection. How this information may be applied in the eradication of African swine fever in Portugal and Spain is discussed.
