The world is currently facing an ongoing coronavirus disease 2019 (COVID-19) pandemic. The disease is a highly contagious respiratory disease which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Current control measures used by many countries include social distancing, wearing face masks, frequent hand washing, self-isolation, and vaccination. The current commercially available vaccines are injectable vaccines, although a few intranasal vaccines are in trial stages. The reported side effects of COVID-19 vaccines, perceptions towards the safety of the vaccines, and frequent mutation of the virus may lead to poor herd immunity. In veterinary medicine, attaining herd immunity is one of the main considerations in disease control, and herd immunity depends on the use of efficacious vaccines and the vaccination coverage in a population. Hence, many aerosol or intranasal vaccines have been developed to control veterinary respiratory diseases such as Newcastle disease, rinderpest, infectious bronchitis, and haemorrhagic septicaemia. Different vaccine technologies could be employed to improve vaccination coverage, including the usage of an intranasal live recombinant vaccine or live mutant vaccine. This paper discusses the potential use of intranasal vaccination strategies against human COVID-19, based on a veterinary intranasal vaccine strategy.
Haemorrhagic septicaemia (HS) is an acute, septicaemic disease of cattle and buffalo of Asia and Africa caused by Pasteurella multocida B:2 or E:2. Buffaloes are believed to be more susceptible than cattle. In this study, 9 buffaloes of 8 months old were divided equally into 3 groups (Groups 1, 3, 5). Similarly, 9 cattle of 8 months old were equally divided into 3 groups (Groups 2, 4, 6). Animals of Groups 1 and 2 were inoculated with PBS while Groups 3 and 4 were inoculated subcutaneously with 10(5) cfu/ml of P. multocida B:2. Animals of Groups 5 and 6 were inoculated intranasally with the same inoculum. Both buffaloes and cattle that were inoculated subcutaneously succumbed to the infection at 16 h and 18 h, respectively. Two buffaloes that were inoculated intranasally (Group 5) succumbed at 68 h while the remaining cattle and buffaloes survived the 72-h study period. Endotoxin was detected in the blood of infected cattle (Group 4) and buffaloes (Groups 3 and 5) prior to the detection of P. multocida B:2 in the blood. The endotoxin was detected in the blood of buffaloes of Group 3 and cattle of Group 4 at 0.5 h post-inoculation while buffaloes of Group 5 and cattle of Group 6 at 1.5 h. On the other hand, bacteraemia was detected at 2.5 h in buffaloes of Group 3 and cattle of Group 4 and at 12 h in buffaloes of Group 5 and cattle of Group 6. Affected cattle and buffaloes showed lesions typical of haemorrhagic septicaemia. These included congestion and haemorrhages in the organs of respiratory, gastrointestinal and urinary tracts with evidence of acute inflammatory reactions. The severity of gross and histopathology lesions in cattle and buffalo calves that succumbed to the infection showed insignificant (p > 0.05) difference. However, inoculated buffalo and cattle that survived the infection showed significantly (p < 0.05) less severe gross and histopathological changes than those that succumbed. In general, cattle are more resistant to intranasal infection by P. multocida B:2 than buffaloes.
Pasteurella multocida B:2 is a Gram-negative organism causing haemorrhagic septicaemia (HS) in buffaloes. It causes severe pulmonary infection, leading to infiltration of numerous macrophages and neutrophils. Despite the inflammatory response, buffaloes succumb to HS. This study aims to evaluate the in-vitro efficacy of macrophages and neutrophils of buffalo following exposure to P. multocida B:2. In-vitro infections were done using 107 cfu/ml of P. multocida B:2 for Group 1, Escherichia coli for Group 2 and Mannhaemia haemolytica A:2 for Group 3 cells. The inoculated cell cultures were harvested at 0, 30, 60 and 120 min post-exposure and the phagocytic, killing and cell death rates were determined. Both phagocytosis and killing rates of all bacteria increased over time. Phagocytosis involved between 71% and 73% neutrophils and between 60% and 64% macrophages at 120 min. Killing rate of all bacteria involved between 76% and 79% for neutrophils and between 70% and 74% for macrophages at 120 min. Death rate of neutrophils ranged between 67% in Group 3, and 88% in Group 1 at 120 min, significantly (p 0.05) than Group 2. Similar pattern was observed for death rate of macrophages. The phagocytosis and killing rates of P. multocida B:2 were similar to other bacterial species used in this study but more neutrophils and macrophages were dead following infection by P. multocida B:2 than M. haemolytica A:2.
Haemorrhagic septicaemia (HS) is an acute septicaemic disease of buffalo and cattle caused by Pasteurella multocida B:2 and E:2. Field outbreaks of HS are known to result in localisation of bacteria in the tonsils of surviving buffalo, confirming that animals can become carriers and the role of respiratory tract in the transmission of the disease. This report describes additional sites of localisation of P. multocida B:2 in surviving buffalo following experimental induction of HS.
Skin abrasions often occur in farmed fish following handling by labourers, injury by farm facilities, cannibalism and ectoparasites. Vibrio spp. are opportunistic pathogens that can invade host fish through damaged tissues and cause outbreaks of vibriosis. This study describes the effect of skin abrasions on the infectivity of V. harveyi using Asian seabass Lates calcarifer (Bloch, 1790) fingerlings as a case example and compares bacterial load and fish survival following immersion challenge with different doses. In total, 315 fish (6.67 ± 1.8 g) were divided into 3 treatments: skin abrasion followed by immersion infection, immersion infection only and an uninfected, uninjured control. Fish in the infection treatments were divided into 3 subgroups and exposed in triplicate to a 7 d immersion challenge with 106, 107 and 108 CFU ml-1 of live V. harveyi. No mortalities were observed in the control and immersion infection groups. However, fish in the skin abrasion treatment group that were infected with 108 CFU ml-1 of live V. harveyi showed signs of progressing disease throughout the experiment, which resulted in mortalities. Significantly higher bacterial loads (p < 0.05) were recorded in the intestine, liver and gills of the fish in this group. Fish in the skin abrasion treatment that were exposed to 107 and 108 CFU ml-1 of V. harveyi showed 100% mortality by Days 5 and 4, respectively. These findings confirm that skin injuries increase the susceptibility of seabass fingerlings to V. harveyi infection.
The genus Aeromonas has been recognised as an important pathogenic species in aquaculture that causes motile Aeromonas septicaemia (MAS) or less severe, chronic infections. This study compares the pathogenicity of the different Aeromonas spp. that were previously isolated from freshwater fish with signs of MAS. A total of 124 isolates of Aeromonas spp. were initially screened for the ability to grow on M9 agar with myo-inositol as a sole carbon source, which is a discriminatory phenotype for the hypervirulent A. hydrophila (vAh) pathotype. Subsequently, LD50 of six selected Aeromonas spp. were determined by intraperitoneal injection of bacterial suspension containing 103, 105, and 107 CFU/mL of the respective Aeromonas sp. to red hybrid tilapias. The kidneys, livers and spleens of infected moribund fish were examined for histopathological changes. The screening revealed that only A. dhakensis 1P11S3 was able to grow using myo-inositol as a sole carbon source, and no vAh strains were identified. The LD50-240h of A. dhakensis 1P11S3 was 107 CFU/mL, while the non-myo-inositol utilizing A. dhakensis 4PS2 and A. hydrophila 8TK3 was lower at 105 CFU/mL. Similarly, tilapia challenged with the myo-inositol A. dhakensis 1P11S3 showed significantly (p < 0.05) less severe signs, gross and histopathological lesions, and a lower mortality rate than the non-myo-inositol A. dhakensis 4PS2 and A. hydrophila 8TK3. These findings suggested that myo-inositol utilizing A. dhakensis 1P11S3 was not a hypervirulent Aeromonas sp. under current experimental disease challenge conditions, and that diverse Aeromonas spp. are of concern in aquaculture farmed freshwater fish. Therefore, future study is warranted on genomic level to further elucidate the influence of myo-inositol utilizing ability on the pathogenesis of Aeromonas spp., since this ability correlates with hypervirulence in A. hydrophila strains.