Cutaneous larva migrans is transmitted via:
Correct Answer D:
Larva migrans is transmitted by skin contact with soil contaminated with hookworm larvae from dog and cat feces in tropical and subtropical areas. Wearing shoes and sitting on a towel rather than directly on the ground are protective measures.
The scabies mite is predominantly transmitted by:
Correct Answer B:
The scabies mite is predominantly transmitted by direct personal contact. Infestation from indirect contact with clothing or bedding is believed to be infrequent. Hats are frequent transmitters of head lice, but not scabies.
Of the following, which one has the greatest potential to spread via human-to-human transmission?
Correct Answer C:
There is a host of microorganisms and their biological products that could be used as agents of mass destruction. The CDC has identified six agents as having a high likelihood for production and lethal dissemination. Yersinia pestis, the organism responsible for pneumonic plague, can induce infection in humans through skin penetration or direct ingestion of fewer than 10 organisms. Patients suspected of having pneumonic plague should be maintained under strict droplet precautions until they have completed 4 days of antibiotic therapy. Person-to-person spread of disease from inhalation anthrax is not known to occur. Neither isolation nor quarantine is required for typhoidal tularaemia, botulism, or Q fever, although standard precautions should be taken.
The fact that avian influenza has affected only a small number of humans is most likely due to:
Correct Answer A:
Human-to-human transmission of the H5N1 avian influenza strain has, to date, been relatively rare and has occurred via means that have not been sustained. Domestic pets, poultry, and swine have been infected and are potential sources of infection. Humans have not developed immunity to this strain as a result of recent epidemics of similar strains.
A man comes to you for genetic counseling. He states there is Huntington disease in his family. His mother is healthy. His paternal grandmother died of it. His paternal uncles all developed it. His father died of a car accident at 35 years of age.
What are the chances this man will develop Huntington disease?
In the above pedigree, red represents Huntington's disease and blue represents normal. The man’s father died at age 35 and he is represented by the square with a cross. Since the age of onset of Huntington's is usually after 35, we do not know if the father had the disease or not. The man himself is indicated by the question mark. The pedigree is labeled with the corresponding alleles.
Huntington's disease is autosomal dominant, needing only one affected allele from either parent to inherit the disease. This generally means there is a one in two chance of inheriting the disorder from an affected parent.
The man's father will get one copy of the recessive allele ‘a’ from his father while his second allele has a 50% probability of being dominant "A" and a 50% probability of being a recessive ‘a’. The man will get one recessive ‘a’ allele from his mother and the other allele depends on his father's genotype. The figures below illustrates the possible genotypes in the man:
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