In this case, it's for a humanitarian/veterinarian expedition to be carried in India by British vet and Indian animal-conservationist Luke Gamble.
For the mission, the Mercedes-Benz Zetros received a special body and auxiliary medical components in England, thus becoming the world's first stand-alone, fully mobile veterinary clinic with off-road capabilities.
The (highly) mobile medical truck has an operating room, pull-out auxiliary units, an independent power supply with backup and all the sanitation facilities you would expect in a vet clinic.
The 27-ton colossus will cover well over 2500 km (1553 miles) across India, during which it will vaccinate at least 50,000 stray dogs against rabies. The “Mission Rabies” expedition is urgently needed since latest studies show that in India one child dies of rabies every hour.