The vector for nagana disease in cattle is

The vector for nagana (African animal trypanosomiasis) in cattle is the tsetse fly (Glossina species). Nagana is caused by protozoan parasites of the genus Trypanosoma (particularly T. vivax, T. congolense, and T. brucei brucei), which are transmitted to cattle and other livestock through the bite of infected tsetse flies.

When an infected tsetse fly bites a healthy animal, it injects trypanosomes into the bloodstream. The disease causes fever, anaemia, weight loss, lethargy, and if untreated, can be fatal. Nagana is a major constraint to livestock production in sub-Saharan Africa, particularly in the tsetse fly belt.

The other options are not vectors for nagana:

• Ticks are vectors for other cattle diseases such as babesiosis (red water), anaplasmosis, and East Coast fever, but not for nagana.
• Roundworms are internal parasites (endoparasites) that cause helminthiasis, not nagana. They are not vectors but pathogens themselves.
• Lice are ectoparasites that cause skin irritation and can transmit some blood parasites, but they are not the vector for nagana.

Exam tip: Tsetse fly transmits trypanosomiasis (nagana in animals, sleeping sickness in humans). This is one of the most frequently tested vector-disease pairings.