DHR - BRET Microbiology PYQs Sept 2024

Virology, Mycology & Immunology

Which of these is not one of the three clinical forms of leishmaniasis

Leishmaniasis presents as visceral kala-azar affecting reticuloendothelial organs, cutaneous with skin ulcers, and mucocutaneous involving nasopharyngeal mucosa. Ocular leishmaniasis is not recognized as a distinct primary clinical form, though secondary ocular involvement may rarely occur.

Ref: Ananthanarayan and Paniker's Textbook of Microbiology, 11th Edition, Chapter on Protozoa Leishmania, discusses three major clinical forms visceral cutaneous mucocutaneous leishmaniasis and notes ocular not classified as primary form, published by Universities Press India.

View Details

Virology, Mycology & Immunology

Major zoonic vector of Eastern equine encephalitis is

Culiseta melanura is the primary enzootic vector maintaining Eastern equine encephalitis virus among passerine birds in swamp habitats. Bridge vectors like Aedes and Coquillettidia transmit to humans and horses. C. melanura ornithophilic feeding sustains enzootic cycle crucial for amplification.

Ref: Service MW, Medical Entomology, and CDC Arbovirus Manual, Chapter on Eastern Equine Encephalitis, describes Culiseta melanura as primary enzootic vector maintaining virus among birds with Aedes as bridge vectors to humans and equines, published by Cambridge.

View Details

Virology, Mycology & Immunology

Plague is transmitted to a person when

Yersinia pestis forms biofilm blocking flea proventriculus. Starved flea attempts to feed and regurgitates bacteria into bite wound from blocked esophagus. This regurgitation mechanism, not saliva injection or fecal contamination, efficiently transmits plague from rodents via Xenopsylla cheopis.

Ref: Prescott's Microbiology, 11th Edition, Chapter on Yersinia and Medical Entomology by Lehane, Chapter on Fleas, discusses Yersinia pestis biofilm blockage of proventriculus in Xenopsylla cheopis leading to regurgitation transmission of bubonic plague, published by McGraw-Hill.

View Details

Virology, Mycology & Immunology

In Hemipterans, what sexes/stages feed on blood

In blood-sucking Hemiptera such as Triatominae and Cimicidae, both nymphal instars and adult males and females require blood meals for molting and reproduction. Unlike mosquitoes where only females feed, all mobile stages and both sexes are obligate hematophages.

Ref: Service MW, Medical Entomology for Students, 5th Edition, Chapter on Hemiptera Triatominae and Cimicidae, explains both nymphs and adult males and females of bedbugs and kissing bugs require blood meals for development and reproduction, published by Cambridge University.

View Details

Virology, Mycology & Immunology

Cat flea larvae feed on

Adult cat fleas feed on host blood and excrete partially digested blood as frass. Larvae are detritivores living in bedding, feeding on this blood-rich adult feces, providing necessary protein and iron for development, not directly feeding on host blood or skin.

Ref: Rust MK, Annual Review of Entomology, Biology of Cat Flea Ctenocephalides felis, and Service MW Medical Entomology Chapter on Fleas, describes larval feeding on adult flea frass blood-rich feces in bedding as obligate diet, published by Cambridge University.

View Details

Virology, Mycology & Immunology

Where does Rickettsia prowazekii propagate in the body louse

Rickettsia prowazekii causing epidemic typhus multiplies intracellularly in gut epithelial cells of Pediculus humanus. Infected epithelium ruptures releasing rickettsiae into feces. Humans acquire infection by scratching infectious louse feces into bite wounds, not via salivary transmission.

Ref: Ananthanarayan and Paniker's Microbiology, 10th Edition, Chapter 40 Rickettsiae, and Prescott's Microbiology, describes Rickettsia prowazekii replication in gut wall epithelium of body louse Pediculus humanus and fecal transmission of epidemic typhus, published by Orient Longman.

View Details

Virology, Mycology & Immunology

Which of the following is not a virus transmitted by mosquitoes

Yellow fever, dengue, and Japanese encephalitis are arboviruses transmitted by Aedes and Culex mosquitoes. Japanese river fever more correctly tsutsugamushi disease or scrub typhus is caused by Orientia tsutsugamushi and transmitted by trombiculid mites, not mosquitoes.

Ref: Knipe and Howley, Fields Virology, 6th Edition, Volume 1 Chapter on Arboviruses Flaviviridae Togaviridae, and Ananthanarayan Microbiology Chapter on Rickettsiae, distinguishes mosquito borne yellow dengue JE viruses versus Orientia tsutsugamushi mite borne scrub typhus, published by LWW.

View Details

Virology, Mycology & Immunology

The pathogen responsible for louse-borne relapsing fever is

Louse-borne relapsing fever is caused by Borrelia recurrentis, transmitted by Pediculus humanus humanus. The spirochete undergoes antigenic variation causing recurrent febrile episodes. Unlike tick-borne Borrelia, it has a degraded genome and is transmitted when crushed louse lice contaminate bite wounds.

Ref: Ananthanarayan and Paniker's Textbook of Microbiology, 11th Edition, Chapter on Spirochetes Borrelia, discusses Borrelia recurrentis louse-borne relapsing fever antigenic variation transmission by Pediculus humanus humanus, published by Universities Press India.

View Details

Virology, Mycology & Immunology

Anoplurans are characterized by (A) Absence of wings (B) Long filiform antennae (C) Only one pair of wings (D) Mouthpart

Anoplura are wingless blood-sucking lice with dorsoventrally flattened bodies. They lack wings completely and possess piercing sucking mouthparts retracted into head when not feeding. Antennae are short, five-segmented, making absence of wings plus retracted mouthparts diagnostic.

Ref: Richards and Davies, Imms' General Textbook of Entomology, Volume 2 Classification and Biology, Chapter on Order Phthiraptera Suborder Anoplura, details wingless nature mouthparts retracted into head and hematophagy of sucking lice, published by Springer Netherlands.

View Details

Virology, Mycology & Immunology

One of the following is a non-blood feeding insect that attacks cattle and causes myiasis Choose the correct answer from

Cochliomyia hominivorax, New World screwworm, adults are non-blood-feeding free-living flies feeding on nectar. Larvae are obligate parasites causing traumatic myiasis in cattle wounds, feeding on living tissue, unlike Stomoxys which is hematophagous blood feeder.

Ref: James MT, James and Harwood's Medical Entomology and Wall and Shearer Veterinary Ectoparasites Biology, Chapter on Myiasis, describes Cochliomyia hominivorax as non-blood feeding adult causing traumatic myiasis versus Stomoxys stable fly hematophagy, published by Wiley.

View Details

Virology, Mycology & Immunology

One of the following is an intermediate host of the nematode Thelazia sp. Choose the correct answer from the following o

Thelazia eyeworms cause thelaziasis in cattle and horses. Their larvae are ingested by non-biting face flies like Musca autumnalis, where they develop to infective L3 in fly tissues, then deposited onto eye conjunctiva during subsequent feeding, completing transmission.

Ref: Taylor, Coop and Wall, Veterinary Parasitology, 4th Edition, Chapter on Nematodes Thelazia and Eyeworms, discusses intermediate host Musca autumnalis face fly development of Thelazia gulosa and rhodesi to L3, published by Wiley Blackwell UK.

View Details

Virology, Mycology & Immunology

Given below are two statements Statement I : Genetic approach of mosquito control can be achieved through SIT-RIDL techn

Genetic control like SIT-RIDL demands extensive mass-rearing, sexing, irradiation, and release infrastructure, not fewer facilities. Additionally, RIDL involves transgenic males carrying tetracycline-repressible lethal system released to mate, killing offspring, not selecting females for release, making both statements inaccurate.

Ref: Alphey et al., Nature Biotechnology and Alphey L, Annual Review of Entomology, and Service MW Medical Entomology, Chapter on Genetic Control, details RIDL tetracycline repressible lethal system using tTA in males and facility requirements for SIT, published by Springer.

View Details