Clinical presentation of FMD virus SAT1 infections in experimentally challenged indigenous South African goats

Effect of physical form of the therapeutic diet on the behaviour of crossbred calves experimentally infected with foot-and-mouth disease virus

The oral lesions associated with foot-and-mouth disease (FMD) negatively affect animal behavior, which can adversely impact animal production and welfare. Physical form of a therapeutic diet (TD) can improve the feed intake and wellbeing during the acute phase of FMD. Accordingly, we tested the effect of two physical forms of a previously developed TD on the behavior of calves experimentally infected with FMD virus (FMDV). Crossbred Holstein Friesian male calves of 10-12 months (n = 12) were experimentally infected with a virulent strain of FMDV and were offered a TD enriched with 19% CP and 2.9 Mcal ME/kg for 11 days post-FMDV infection. One group received the TD in mash form (TD_M) while the other (n = 6/group) received it in cooked form (TD_C). A group of four calves served as uninfected control and were fed TD_M. The time spent by the calves on certain behaviours was recorded in a pre-set form from 06:00-18:00 h for 10 days from day 2-11 post-FMDV infection. The data was divided into two sessions. Session 1 (06:00-13:00 h) represented after the offering of TD, while session 2 (13:01-18:00 h) represented the data after offering green fodder. Based on exploratory data analysis, data recorded from day 2-7 post-FMDV infection was included in the final analysis. Linear mixed model was used by fitting treatment, day and their interaction as fixed effects while calf as random effect. Orthogonal contrast was applied by comparing the infected TD_M with other two groups. The results revealed that the cooked form of TD improved the ingestion time, resting time, sleeping time and licking time from day 2-7 post-FMDV infection as compared with the infected TD_M group. Ingestive behaviour was better in the infected TD_C than that of TD_M group (p < 0.01). The sleeping time was significantly high in the infected groups as compared to the uninfected TD_M group (p < 0.01) till day 6 post-FMDV infection. Daily activities such as licking, standing and resting differed significantly between the infected TD_M and TD_C groups in session 1, but not in session 2. Urination and defecation did not differ significantly between the infected TD_M and TD_C groups. It was concluded that cooked form of TD remediated the effects of infection with FMDV as evidenced by improvement in the behaviour of the calves.

Experimental Infection of Foot and Mouth Disease in Indian Sheep and Goats

Foot-and-mouth disease (FMD) is an economically important contagious disease of livestock mainly cattle, buffalo, sheep, goats, and pig. There is limited data available on pathogenesis of foot and mouth disease in goats. In the study, the sheep and goats were infected experimentally with a serotype O foot-and-mouth disease virus by different challenge routes. The sheep and goats challenged by coronary band route and coronary band and intra-dermo-lingual route exhibited FMD clinical signs at 2-5 days post challenge. Whereas intra-dermo-lingual challenged sheep and goats did not exhibit FMD clinical signs. Live virus could be isolated from blood of infected sheep and goats at 2-5 days post challenge. Viral RNA could be detected from blood of infected sheep and goats at 1-10 days post challenge. The neutralizing antibody titre was detected at 10 days post challenge and maintained up to 35 days post challenge in all infected sheep and goats. Non structural protein (NSP) antibodies were detected as early as 5-10 days post challenge and remain positive up to 35 days post challenge in the infected sheep and goats. In conclusion, the pathogenesis of sheep and goats with serotype O foot and mouth disease virus by different challenge routes could be demonstrated.

Efficacy of a foot-and-mouth disease vaccine against a heterologous SAT1 virus challenge in goats

Goats are susceptible to infection with foot-and-mouth disease virus (FMDV), but their role in the epidemiology of the disease and response to vaccination is poorly understood. In southern Africa, FMDV serotypes Southern African Territories (SAT) 1, 2 and 3 are known to be endemic. In this study, we evaluated the efficacy of a pentavalent FMD vaccine in goats against heterologous challenge with a pool of field SAT1 FMDV. Forty FMD sero-negative goats (6-12 months of age) of mixed sexes were randomly allocated to one of five treatment groups: full cattle dose (2 ml), 1/3rd (0.67 ml), 1/6th (0.33 ml), 1/12th (0.16 ml) or unvaccinated placebo control. Goats were vaccinated with an inactivated pentavalent FMD vaccine containing serotypes SAT1, SAT2 and SAT3 on day 0 and revaccinated at day 20 post vaccination. Thereafter, thirty-four goats were challenged by tongue inoculation at day 41 post-vaccination using 10^4.57 50% tissue culture infective dose (TCID₅₀) FMDV SAT1 pool. Animals were examined daily and clinical signs were scored. Rectal temperatures were measured daily, with temperatures ≥40 °C defined as fever. Clinical specimens (nasal, oral and rectal swabs) were collected on days 0, 2, 4 and 6 post challenge. Viral shedding was determined using reverse-transcriptase real-time PCR. None of the goats vaccinated with the full cattle dose developed secondary lesions. All vaccinated groups had lower temperatures compared to the unvaccinated controls (P < 0.001). Based on RT-PCR results, goats in the unvaccinated control group shed more virus compared to all groups except for 1/12th (P < 0.05), while goats in the full dose group shed less virus than goats in the 1/12th and the unvaccinated control group (P < 0.05). The results suggest that the 1/3rd (0.67 ml) dose of the vaccine is sufficient to reduce viral shedding after heterologous challenge with a FMDV SAT1 pool.

Impact of foot-and-mouth-disease on goat behaviour after experimental infection with serotype SAT1 virus

Infectious diseases and parasitic infestations can cause a set of non-specific clinical signs, such as increased body temperature and resting, and a decrease in food intake. These physiological and behavioural changes have an adaptive function facilitating defences against the pathogen and to support immune functions. These so-called' sickness behaviours' can also be used as an early detection tool for disease. Foot-and-mouth disease (FMD) still causes great economic losses in endemic countries, especially to smallholder farmers. The aim of this study was to determine if behavioural changes in goats can be used as an early indicator of FMD virus (FMDV) infection. The efficacy of a Southern African Territories (SAT) FMD vaccine was studied on forty South African indigenous goats. Changes in daily activities (resting, feeding, walking), as well as social behaviours (social resting, social feeding, dominance behaviours) were recorded and then compared over time and between clinically affected and unaffected goats. Pedometers were used to estimate average daily steps and to compare between groups of study animals. Eleven goats developed clinical signs of FMD, as well as non-FMD related sicknesses during the course of the study. Overall walking and resting behaviours were not significantly affected by the presence of FMD related clinical signs (p > 0.05). However, during the time of FMDV infection, social resting increased significantly (p < 0.001). Although goats developed FMD lesions on lips and tongues, percentage of time feeding was not affected (p = 0.762), suggesting that the study goats did not perceive the oral lesions as an important disturbance. Similarly, the number of steps did not consistently decrease in the presence of FMD-associated foot lesions. When affected by non-FMD related sicknesses, animals did not have an overall reduction in the time spent feeding (p = 0.867). However, goats affected with non-FMD conditions reduced the amount of social feeding (p = 0.002), potentially avoiding energetically costly competition at the feeding points. Overall, goats affected with FMD did not show more sickness behaviour, suggesting that FMDV infection in goats might not lead to obvious and therefore, easily detectable behavioural changes. This might have implications for farmers and animal health personnel, as individual goats infected with FMDV might be undetected within a flock due to the absence of obvious sickness behaviours, and the virus can therefore be spread more easily between herds through animal movements.