(a) Name two diseases of livestock that can be spread through contaminated drinking water. [2] (b) Describe three methods a farmer can use to purify water b...

(a) Two livestock diseases spread through contaminated drinking water (any two for [2]):

1. Liver fluke disease (fascioliasis) [1]
2. Salmonellosis [1]

Also acceptable: leptospirosis; coccidiosis; blue-green algae poisoning.

(b) Three methods to purify water before giving it to livestock (each described for [2], total [6]):

1. Chlorination - add a measured amount of chlorine solution (e.g. sodium hypochlorite/bleach) to the water. The chlorine kills bacteria, viruses and many parasites by damaging their cell membranes. The correct dose must be calculated to ensure effective disinfection without leaving harmful residues [2].
2. Sand filtration - pass the water through a slow sand filter (layers of graded sand and gravel). As water percolates downward, suspended solids, some bacteria and parasites are physically trapped in the sand matrix and biologically degraded by a biofilm on the sand grains [2].
3. Sedimentation - allow untreated water to stand undisturbed in a tank or settling basin. Suspended soil particles, organic debris and some heavier pathogens settle to the bottom over several hours. The clearer upper water is then decanted for use [2].

Also acceptable: boiling (kills most pathogens, practical for small volumes); UV treatment (ultraviolet light destroys microbial DNA).

(c) Why young calves are more at risk from waterborne diseases:

1. Young calves have an immature immune system that is still developing, so they produce fewer antibodies and immune cells to fight off infection [1].
2. They have not yet built up acquired immunity through prior exposure to common environmental pathogens, unlike adult cattle that have encountered and developed resistance to many waterborne organisms over their lifetime [1].

(d)(i) Two immediate steps for the farmer (any two for [2]):

1. Remove cattle from the pond immediately and fence off access to prevent further exposure to the contaminated water [1].
2. Call a veterinarian to examine and treat the affected animals, which may need rehydration therapy and antimicrobial treatment depending on the cause [1].

Also acceptable: collect a water sample for laboratory analysis; provide alternative clean water immediately.

(d)(ii) How to provide a clean alternative water supply (3 marks):

1. Set up a temporary water trough in a clean area away from the contaminated pond [1].
2. Fill it with water from a borehole, piped supply or transported clean water from a tested source [1].
3. Position the trough in a shaded area to slow algal growth and evaporation, and establish a schedule for regular refilling to ensure a continuous supply until the pond is decontaminated and re-tested [1].