North American Veterinary Licensing Examination (NAVLE) Practice Test

Which condition is characterized by a high mortality rate in young birds presenting with weakness and diarrhea?

1. Avian spirochetosis

2. Salmonella pullorum

3. Histomoniasis

4. Campylobacter jejuni

The correct answer is: Salmonella pullorum

The condition associated with a high mortality rate in young birds experiencing weakness and diarrhea is Salmonella pullorum. This disease, commonly known as pullorum disease, primarily affects young chicks and is caused by the bacterium Salmonella enterica serovar Pullorum. The presentation of weakness and diarrhea is indicative of systemic infection and can lead to significant morbidity and mortality in susceptible populations, particularly in poultry. Salmonella pullorum infects the gastrointestinal tract and can spread systemically, resulting in septicemia. Diagnosis is often based on clinical signs, history, and confirmatory testing. The high mortality rate is attributed to the rapid progression of the disease and the young birds' limited immune response, making prevention through biosecurity measures and vaccination vital in a flock. Other conditions listed may cause similar clinical signs but vary in morbidity and mortality rates or populations affected. For example, while avian spirochetosis can affect birds and lead to severe disorders, it does not typically result in as high a mortality rate in young chicks as pullorum disease. Histomoniasis is primarily a concern in turkeys and is caused by a protozoan parasite, which again does not fit the profile as closely as Salmonella pullorum. Similarly, Campylobacter jejuni is more