A complement fixation technique for the quantitative measurement of antigenic differences between strains of the virus of foot-and-mouth disease

SUMMARYAn outbreak of foot-and-mouth disease in a partially immune population of cattle in Botswana is described. The results show that when cattle immunized by vaccination were presented with natural field challenge of FMD, many animals with immunity sufficient to protect them against clinical disease were, however, susceptible to pharyngeal infection and subsequently became virus carriers. The proportion of animals becoming carriers appeared to vary with the degree of severity of the challenge.Vaccination before exposure to virus appeared to have little effect on the duration of the carrier state. No evidence was obtained of the spread of carrier virus to immune herds following the outbreak.Antibody titres during the outbreak were higher in the clinically infected animals than in the carrier animals and the uninfected animals. Evidence suggested that natural challenge boosted the titres of immune animals. After the outbreak, however, it was not possible to distinguish by their antibody titres between the carrier animal and the virus-negative animal.Antigenic studies on the strains of virus isolated are described.

Section: Virus Specificitymentioning

confidence: 99%

Section: Antigenic Studiesmentioning

confidence: 99%

Observations on the carrier state and related antibody titres during an outbreak of foot-and-mouth disease

Hedger

1970

“…Two of the viruses isolated were adapted to guinea-pigs for specific antiserum production and antigenic differences were studied between these viruses and previously known subtype strains by cross-complement-fixation tests, using the method described by Davie (1964) in addition to the microtitre method.…”

Section: Virus Specificitymentioning

confidence: 99%

“…Specific guinea-pig antisera were prepared to both those carrier strains, and cross-complement-fixation tests (Davie, 1964) were carried out in tubes with these strains, the outbreak strain and the vaccine strain. Table 4 illustrates the relationship of these virus strains to each other expressed as cross-fixation products.…”

Section: Serologymentioning

confidence: 99%

The isolation and characterization of foot-and-mouth disease virus from clinically normal herds of cattle in Botswana

Hedger

1968

SUMMARYThe results of a survey of the foot-and-mouth disease carrier state in three localities of an FMD enzootic area of Botswana are presented. The collection, storage and handling of the samples is mentioned and the isolation of virus on calf thyroid monolayer tissue cultures is described. Type SAT 3 virus was isolated from up to 20% of the animals sampled at periods between 7 and 12 months after natural infection. Sera were tested for all the animals from which virus was recovered and compared with similar numbers of sera from virus-negative animals. No correlation was found between the carrier state and serum antibody titres.Antigenic studies are described which indicated not only an antigenic variation of some carrier viruses isolated from the outbreak strain but also antigenic differences between strains of carrier virus from different animals in the same herd. There was no evidence at the time of sampling of the persistence as carrier virus of the attenuated vaccine strains of FMDV used previously in the cattle sampled.The results suggest that transference of carrier virus from animal to animal may occur in the absence of clinical infection.

“…ra x rb (or r1 x r2). Davie (1964) classified strains of CFP > 0.5-1.0 into the same subtype, while those of CFP < 0 5 were considered to be different.…”

Section: Complement-fixation Testmentioning

confidence: 99%

Variation among strains of type A foot-and-mouth disease virus in the Eastern Mediterranean region 1964–1972

Arrowsmith

1975