Cholera is a life-threatening and infectious disease caused by the bacterium Vibrio cholerae. One of the symptoms of the disease is severe diarrhoea. V. cholerae O1 and V. cholerae O139 are the two forms of the pathogen that are associated with cholera epidemics (large outbreaks). These two forms have different antigens that can be detected.

Mark scheme

Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.

1. [2] any two from: oral rehydration (salts / solution / therapy) ; A ORS / ORT A rehydration therapy if ref. to 'drinking' stated within response
2. [2] solution of/ water with, glucose and salts ; A named example for salts e.g. sodium / potassium / citrate / chloride
3. [2] AVP; e.g. antibiotics / doxycycline / tetracycline / furazolidone / choramphenicol / sulfaguanidine (standard treatment in some countries) zinc treatment (standard treatment for children in some countries) ref. to isolation
4. [2] any two from: decreases, recovery time; A cured more quickly I helps recovery / reduces severity of disease
5. [2] reduces time of /stops, diarrhoea production (containing pathogen);
6. [2] less likely to / AW, contaminate water ; reduced transmission of pathogen; AW e.g. breaks transmission cycle
7. [2] allow antibody or mAb or Mab for monoclonal antibody I ref. to receptor I active site I combines / bonds any two from: specific / different, (Vibrio / pathogen) antigen-binding sites / binding sites for antigen; R if antibody described as enzyme A (each) mAb binds to a, specific / particular, (Vibrio / pathogen) antigen
8. [2] (each mAb has) specific / different, tertiary structure / variable region(s) / primary structure / sequence of amino acids ;
9. [2] binding site and antigen have complementary shapes ;
10. [3] allow antibody or mAb or Mab for monoclonal antibody any three from: 1 person A, has cholera O1 / is infected with V. cholerae 01 and person B, does not have cholera ; A ref. to person A testing positive for cholera 01 and person B testing negative to cholera
11. [3] 2 tests are, valid / working, because, controls / bands 4, shows bands ;
12. [3] person A, band/colour in area 3 because 3 anti-01 (mobile) antibody binds (specific antigen on) Vibrio 01 ; A antigen-antibody (complex) 01 formed
13. [3] 4 antigen-antibody (complex) 01 binds to immobilised antibody ref. to area 3; R if stated as, band / colour, in area 2
14. [3] 5 person B (in test area 2 and 3) no bands form / no colour / no change, because no antibody binds with antigen / no antigen-antibody complexes formed;
15. [1] 95 / 95.1 (%); R 95.0%
16. [1] I ref. to, cheaper / no need for (highly) trained personnel / easier to use / easier to obtain results / accurate R more accurate any one from: quicker to, obtain result / to do the test ; A less time consuming can carry out test in a greater variety of places / AW ; e.g. can be done at home less labour intensive ; AW e.g. only needs one person / can do it yourself easier to test more people at one time / AW ; portable; AVP; e.g. idea of easier to transport or distribute (to reach more people) ref. to, safer/less risk, from pathogen available to more people (consequence of cheaper) suggestion that dipsticks are able to identify different, forms / strains