Pneumocystis

Question 1

What is the etiologic agent of pneumocystosis?

Answer 1

Pneumocystis carinii
Pneumocystis jiroveci

Question 2

What is the primary habitat of Pneumocystis spp. in mammals?

Answer 2

The mammalian lung.

Question 3

Most reports of clinical P. carinii pneumonia are linked with documented or suspected ______________

Answer 3

Cell-mediated immunodeficiency in the host.

Question 4

Phylogenetic classification based on 16S-like rRNA sequences indicates that P. carinii is most closely related to which class of organisms?

Answer 4

Fungi of the class Ascomycetes.

Question 5

The species of Pneumocystis now designated to infect people is named:

Answer 5

Pneumocystis jiroveci.

Question 6

The primary mode of spread for Pneumocystis carinii is thought to be?

Answer 6

Airborne droplet transmission between hosts.

Question 7

A higher prevalence of Pneumocystis infection has been found in dogs with which concurrent disease?

Answer 7

Canine distemper.

Question 8

Where in the host’s body is the entire life cycle of P. carinii completed?

Answer 8

Within the alveolar spaces of the lungs.

Question 9

The overgrowth and clustering of P. carinii within alveolar spaces primarily lead to?

Answer 9

Alveolocapillary blockage and decreased gaseous exchange

Question 10

Most canine cases of pneumocystosis have been reported in which breed and age group?

Answer 10

Miniature Dachshunds younger than 1 year.

Question 11

What type of immunodeficiency has been suspected in affected miniature dachshunds with pneumocystosis?

Answer 11

Common Variable Immunodeficiency (CVID).

Question 12

What are some of the observed immunological abnormalities in affected miniature dachshunds with pneumocystosis?

Answer 12

Deficiency of serum IgA, IgG, and IgM.

Question 13

The clinical features of pneumocystic pneumonia in dogs are similar to those caused by other pulmonary pathogens EXCEPT for:

Answer 13

Dry lung sounds, nonproductive cough, and low-grade or absent fever.

Question 14

What is a typical clinical history of pneumocystosis in dogs?

Answer 14

Gradual weight loss and respiratory difficulty progressing over 1 to 4 weeks.

Question 15

Despite weight loss, what is often maintained in most dogs with pneumocystosis?

Answer 15

Good appetite.

Question 16

What is a common abnormality on physical examination of dogs with pneumocystosis?

Answer 16

Dyspnea, tachycardia, and increased dry respiratory sounds.

Question 17

What dermatologic changes may dogs with pneumocystosis show?

Answer 17

Superficial bacterial pyoderma and demodicosis.

Question 18

Pneumocystis carinii is sensitive to drugs used to treat sporozoan infections but resistant to most ______

Answer 18

Antifungal drugs.

Question 19

If an adequate immune response occurs, the body may eliminate Pneumocystis infection, but the removal of large numbers of organisms and cellular debris may take up to _____

Answer 19

8 weeks.

Question 20

In dogs, pneumocystosis has also been reported in adult dogs of which specific breed(s)?

Answer 20

Cavalier King Charles Spaniels
Yorkshire Terrier
Shetland sheepdog

Question 21

Where are the pathologic findings in pneumocystosis primarily confined?

Answer 21

Lungs

Question 22

On gross examination, what is a characteristic appearance of the lungs in a dog with pneumocystosis?

Answer 22

Firm, consolidated, and pale brown or gray, not collapsing when the chest is opened.

Question 23

If cardiac enlargement is present in pneumocystosis cases, it has been primarily ________

Answer 23

Right-sided.

Question 24

Why does routine hematoxylin and eosin (H&E) stain not readily demonstrate P. carinii organisms?

Answer 24

It only demonstrates the nuclei of intracystic sporozoites and trophozoites, not the full organisms.

Question 25

Which special stain is used to stain the cyst walls of P. carinii brownish-black, but does not detect trophozoites?

Answer 25

Methenamine silver staining

Question 26

In histologic examination, alveolar spaces are often filled with cohesive aggregates of amorphous, foamy, eosinophilic material that has a: a) Starburst pattern. b) Linear pattern. c) Honeycomb-like pattern. d) Solid, dense appearance.

Answer 26

Honeycomb-like pattern.

Question 27

What type of cells are typically absent in the alveolar spaces filled with Pneumocystis organisms?

Answer 27

Polymorphonuclear leukocytes.

Question 28

In chronic Pneumocystis infections, especially after treatment, what might cause thickening of alveolar septa?

Answer 28

Fibrosis.

Question 29

Trophozoites in tissue sections and smears are best demonstrated with which stain?

Answer 29

Giemsa stain.

Question 30

Despite their close genetic resemblance to fungi, Pneumocystis organisms are most sensitive to drugs used to treat _________

Answer 30

Protozoal infections.

Question 31

Which two major chemotherapeutic agents have been successfully used to treat pneumocystosis?

Answer 31

Pentamidine isethionate and the combination of trimethoprim and sulfonamide (TMS).

Question 32

What is a major side effect of pentamidine isethionate that requires daily monitoring of serum urea nitrogen and glucose?

Answer 32

Impaired renal function and hypoglycemia.

Question 33

In people, aerosolized delivery has been the preferred route for pentamidine administration. What was the side effect of IM administration in a successfully treated dog?

Answer 33

Localized pain at the injection site.

Question 34

What was a suspected side effect that led to discontinuation of TMS medication in one successfully treated Cavalier King Charles Spaniel?

Answer 34

Nonregenerative anemia suspected from folate antagonism.

Question 35

Why is folic acid supplementation sometimes given with TMS therapy?

Answer 35

To avoid myelosuppression, especially during long-term treatment.