MODES OF TRANSMISSION OF CAPRINE ARTHRITIS-ENCEPHALITIS VIRUS-INFECTION

A single feeding of milk containing 2 x 10(7) TCID50 of infectious cap rine arthritis-encephalitis virus (CAEV) infected 50% of newborn kids. Lesser amounts were not infectious when given as a single ingestion, indicating that 2 x 10(7) TCID50 was near the minimal infective oral d ose. Seroconversion following intravenous innoculation of infectious C AEV was observed to occur more rapidly (4 weeks post-innoculation), at a lower level of exposure (2 x 10(6) TCID50), and more efficiently (1 00%) when compared to other routes of exposure. The occurrence of mate rnal-fetal transmission was supported by experiments in which kids wer e removed from their mothers immediately at birth and reared in isolat ion on virus-free milk or milk replacers. Five percent of a group of 4 0 kids born to naturally CAEV-infected does and handled in this manner seroconverted within 8 weeks. This indicated that at least two kids i n the group were infected prior to birth or during the birth process. When seronegative kids were housed in intimate contact with CAEV-infec ted animals, an additional 10% became seropositive within 20 weeks, su ggesting that contact transmission of CAEV also occurs later in life b etween infected and susceptible goats. Intramammary infusion of 2 x 10 (7) TCID50 infectious CAEV resulted in seroconversion in three of thre e lactating seronegative does within 4-8 weeks post-infusion. Thus, go ats may be infected by a single oral exposure to infectious CAEV, by c ontact with infected individuals as occurs in normal husbandry practic es, by intramammary route as might occur during routine machine milkin g of lactating does, and from doe to fetus either prior to or during t he birth process. Control of CAEV on commercial goat dairies will be e nhanced by incorporation of the findings of these studies in a prevent ive program.