Studies on the carrier state of cattle exposed to foot-and-mouth disease virus

Abstract

Cattle infected with FMDV strains of different epizootiological origin developed a carrier state which persisted in the majority of animals for several months. Fluid samples taken from the oesophageal/pharyngeal region were assayed for infectivity by plaque counts on BHK monolayer cultures and by mouse inoculation. With one strain of virus, infectivity levels of up to 1000 pfu/ml. were recorded for several weeks after infection but in general the virus content of samples was below 50 pfu/ml.The sites of virus persistence and multiplication were identified by titration of suspensions of mucosae and epithelia taken post mortem. Virus was recovered from 41 of 54 cattle killed 14–196 days after infection. The chief sites of virus multiplication based on the frequency of virus recovery and infectivity titres were the dorsal surface of the soft palate and the pharynx. Virus was recovered less frequently from the ventral surface of the soft palate and the glosso-epiglottic space and only occasionally from the tonsillar sinuses, tonsils, tongue, trachea and oesophagus. No virus was detected in the turbinates or in the epithelium of the urinary bladder.

Characterisation of a SAT-1 outbreak of foot-and-mouth disease in captive African buffalo (Syncerus caffer): Clinical symptoms, genetic characterisation and phylogenetic comparison of outbreak isolates

“…In cattle the virus levels in the oesophageo-pharyngeal region begin to decline soon after infection (Burrows, 1966 andDonaldson et al, 1981) and the levels may fluctuate with virus detection becoming erratic by six months post infection (Gebauer et al, 1988 andVan Bekkum et al, 1959). In excess of 50% of cattle that had recovered from infection become persistently infected (Kitching, 2002).…”

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

“…Oesophageal/pharyngeal samples are alkaline and in previous work it had been found that their addition to phosphate buffered saline (PBS) (Burrows, 1966;van Bekkum, Straver, Bool & Frenkel 1966) have noted that oesophageal/pharyngeal samples quickly lose their infectivity when stored at 40 C. and -200 C., comparative parallel tests of oesophageal/ pharyngeal samples containing minimal virus stored at 40 C. and in dry ice at -70°C. were carried out at Pirbright before the field survey.…”

“…Suitmoller & Gaggero (1965) were able to recover FMD virus from the oesophageal fluid of cattle on a farm some months after natural infection, and Burrows (1966), working with experimental cattle, was able to show that the main sites of carrier virus multiplication were the mucosae of the pharynx and the dorsal surface of the soft palate.…”

Growth of foot-and-mouth disease virus in the upper respiratory tract of non-immunized, vaccinated, and recovered cattle after intranasal inoculation

“…Cattle vaccinated with inactivated FMD virus vaccines have become infected after upper respiratory exposure even to homologous virus subtypes (VanBekkum, Frenkel, Frederiks & Frenkel, 1959;Hyslop, 1965a;Burrows, 1966;Sutmoler et al 1968;McVicar & Sutmoller, 1969). For a study of early growth of FM1D virus in immunized cattle, steers were vaccinated and inoculated intranasally after varying periods of time, and pharyngeal virus growth curves were obtained.…”