Veterinary Parasitology

Oviposition sites of equine bot flies (genus Gasterophilus):

• Gasterophilus intestinalis (Common horse bot fly): Females glue their yellowish eggs primarily to the hairs of the forelegs, particularly around the fetlock joint, knees, and the shoulders / scapular region. The eggs require warmth and moisture stimulated by the horse's licking to hatch.
• Gasterophilus nasalis (Throat bot fly): Deposits yellowish-white eggs on hairs of the intermandibular space (between the rami of the mandible).
• Gasterophilus haemorrhoidalis (Nose bot fly): Glues dark brownish-black eggs to the fine hairs of the lips and around the mouth.
• Gasterophilus pecorum: Lays black eggs on pasture grasses and stable fittings.
  
  Option analysis:
• (Fetlock and scapular region): Correct. Primary oviposition sites for Gasterophilus intestinalis.
• Oviposition site for Gasterophilus nasalis (throat bot).
• Oviposition site for Gasterophilus haemorrhoidalis (nose bot).
• Incorrect oviposition site.

Epidemiology of zoonotic parasites in the Indian context:

• Cryptosporidium parvum (A): A well-documented zoonotic apicomplexan protozoan in India. Young dairy calves and ruminants act as major reservoirs shedding infective oocysts that infect human handlers and contaminate drinking water supplies.
• Sarcoptes scabiei (D): Sarcoptes scabiei var. canis and varieties from other domestic animals routinely cause zoonotic pseudo-scabies / sarcoptic acariasis in human contacts.
• Trypanosoma gambiense (B): Causes West African sleeping sickness (transmitted by tsetse flies, Glossina), which does not exist in India.
• Leishmania donovani (C): In the Indian subcontinent (Bihar, West Bengal, Jharkhand), visceral leishmaniasis (Kala-azar) is anthroponotic (human-to-vector sandfly Phlebotomus argentipes-to-human transmission) without an animal reservoir, distinguishing it from zoonotic Leishmania infantum found in the Mediterranean.

Option analysis:
(A) CoxAbic is a maternal coccidiosis subunit vaccine containing affinity-purified gametocyte antigens GAM56 and GAM82 of Eimeria maxima.

Principle of the Sabin-Feldman dye test for Toxoplasma gondii:

• Statement (I) is true: The Sabin-Feldman dye test is considered the historic serological gold standard method for diagnosing toxoplasmosis, possessing very high sensitivity and specificity.
• Statement (II) is false: In this test, live Toxoplasma tachyzoites are incubated with patient serum and complement ('accessory factor'). If specific anti-Toxoplasma antibodies are present, the complement cascade damages the parasite cell membrane, causing the tachyzoites to lose their affinity for alkaline methylene blue; therefore, unstained (colorless/lysed) tachyzoites indicate a POSITIVE test. Conversely, in a negative test (no antibodies), intact tachyzoites avidly take up the stain and appear deeply blue.