Eelke is sometimes referred to as Mr. Mannheimia along the corridors. "That's because I am very much involved in research into polyserositis (inflammation of the pleura and peritoneum in calves) caused by the bacterium Mannheimia haemolytica," says Eelke with a smile.

In healthy animals, Mannheimia haemolytica is found in the nasopharynx and in the area surrounding the tonsils. However, if such animals experience acute stress, or if their resistance has been weakened by infection, bacteria can multiply explosively in the upper respiratory tract. Some of the bacteria then move into the deeper lung tissue, where they encapsulate, making them untreatable with antibiotics. Should a further stressful moment ensue, these bacteria are likely to enter the blood, where they can rapidly cause pneumonia and pleural effusion (polyserositis).

Effective action against polyserositis remains complicated. Because there is a relatively short period of time between the onset of symptoms in calves and their potential loss, veal farmers have been experiencing difficulty to interve in time. Van der Wal: "In 2020, sector research on the genetic composition of Mannheimia haemolytica was carried out through the Animal Health Service. As a result, we have been able to see that there is little genetic variety in the bacteria that lead to polyserositis. We also observed an increase in Mannheimia isolates (cultures) that were unresponsive to different groups of antibiotics."

Polyserositis has two main causes. Due to permeable lungs, or intestines that are excessively so, bacteria can penetrate a calf's bloodstream, subsequently causing infection. Eelke has also seen success in the intestinal approach to polyserositis: ''Through targeted feeding measures, we have been able to greatly reduce polyserositis caused by intestinal bacteria. Our veal farmers and regional managers should be commended for this: thanks to excellent cooperation between both parties, the proportion of intestinal infections in our chain has been significantly reduced."

He continues: "Although the 2020 study has helped us learn more about this particular type of bacterium, we still don't know how polyserositis develops in the calf. Similarly, we are unable to resolve the explosive multiplication of bacteria as of yet." Which is why the Dutch veal industry is to commence a follow-up study in 2022, a collaboration in which GD (Animal Health Service), Denkavit and VanDrie Group, among others, take the lead. This study will look at the influence of farm and animal factors, as well as the effect farmers and their advisors have on the occurrence of new outbreaks of polyserositis, but especially on its prevention.

This investigation will not just look into calf husbandry, with findings from dairy farming and calf husbandry regarding Mannheimia haemolytica set to be shared on both sides. For example, this forthcoming study will use typing of isolates from previous studies conducted by both sectors. Eelke: ''Studies like this one contribute to the insight and action perspective of both dairy and veal farmers. Working together to further improve the health of both calf and cow is crucial''.

I hope it will provide insights and useful tools for calf farmers, regional managers and vets, so that we can continue to work towards the greater goal: a high level of animal health and welfare in our chain, with as little disease and loss as possible," Eelke says in conclusion.