It’s not often that you hear a speaker at a cattle health congress talk primarily about dogs, but that’s just what German researcher Carola Fischer-Tenhagen did. Surprisingly, the crowd at the World Buiatrics Congress, held in Dublin, Ireland, didn’t boo her of the stage. Rather, they listened attentively as what she had to say was both new and intriguing.
Diagnosis of clinical mastitis is fairly straightforward these days, but identifying the specific pathogens that cause the disease can be challenging. “Even having on-farm culturing systems, it takes at least 2 hours,” pointed out Fischer-Tenhagen. “So this puts us in the dilemma of still feeding cows antibiotics without exactly knowing what pathogen we are fighting against.”
Why do we do this, she asked. Because the success of the treatment depends on how early we start.
In a study conducted at Hanover University in Germany, Fischer-Tenhagen and her team wanted to prove that bacteria-causing mastitis in dairy cows could be identified by their odour. To do this, they trained scent dogs to discriminate the odour of Staphylococcus aureus against five other common mastitis-causing agents.
In the first experiment the dogs were tested to see if they could discriminate S. aureus in the headspace of blood agar plates with growing colonies. Then, the dogs had to identify the odour of S. aureus in spiked milk samples.
Eight dogs completed the training and took part in the test, said Fischer-Tenhagen. Training didn’t take long either. Times ranged between 111 to 290 minutes, she said.
Overall, the dogs were successful in identifying S. aureus in the head space of agar plates against five other common mastitis-causing agents, including Escherichia coli, Streptococcus uberis and Streptococcus dysgalactiae. Overall sensitivity was 91.3%, said Fischer-Tenhagen, and specificity was 97.9%.
Each dog tested 100 samples; four dogs made no mistakes.
In the bulk tank milk experiment, the dogs were able to identify S. aureus against Strep uberis and Enterococcus spp. with a specificity of 82% and 87% respectively.
These results were positive enough for Fischer-Tenhagen to conclude that odour detection could be used as a diagnostic tool for mastitis pathogens.
“Maybe you have a heat [estrous] detection dog on farm that is getting bored, and maybe you train him to be a mastitis dog as well,” she concluded.