Infectious Diseases Immunology

1. Infectious DiseasesImmunology LATG: Chapters 10-11

2. Health Maintenance • Maintaining lab animal health requires • Proper environment. • Proper food and water. • Disease prevention program. • Disease detection program. • Contingency plan if disease is detected.

3. Disease Prevention • Type of program depends upon species. • Rodents--primarily review of vendor data and procedures in place to prevent introduction and spread of disease. • Nonrodents--As for rodents but may also have other facets such as vaccinations, dewormings etc.

4. Disease Detection • Like NORAD, PADDS (Pfizer Animal Disease Detection System) relies on • Early warning system--technicians who check animals daily. • Early response--veterinary technicians who evaluate reported problems. • Final response--delivered after evaluation and consultation with veterinarian and PI.

5. Disease Detection • A rodent sentinel program is in place to screen for potential viral, bacterial and parasitic contaminants. • In the rare instance of an actual infection steps are taken to evaluate the extent of the infection and eliminate it.

6. Pathogenic Organisms • Life forms that have the potential to cause disease under the proper conditions. • Text classifications • Bacteria • Fungi • Viruses • Parasites

7. Biology Influencing Organisms • In laboratory animal science we are also very concerned with biology influencing organisms. • These organisms may or may not cause clinical disease. • Biological systems can be influenced even by subclinical infections.

8. Viruses • Small particles made up of nucleic acid and a protein capsule. • Viruses may also be covered by an envelope • Many viruses can infect laboratory animals, most do not cause clinical disease. • Viruses are divided into two main classes. • DNA viruses • RNA viruses

9. DNA Viruses of Mice • Mousepox (Ectromelia) • Minute virus of mice • Cytomegalovirus • Polyoma virus • Mouse parvo virus

10. DNA viruses of rats • Polyoma virus (in nude rats) • Adenovirus • Kilham rat virus • Rat parvo virus

11. RNA viruses of mice • Mouse hepatitis virus (MHV) • Sendai • Lymphocytic choriomeningitis • Reovirus • Hantavirus • Retroviruses--mouse leukemia virus and mouse mammary tumor virus

12. RNA viruses of rats • Sialodacryoadenitis virus (SDAV) • Sendai • Pneumonia virus of mice • Hantaan virus

13. Bacteria • Many bacteria in nature are beneficial. • In nearly all mammals there are more bacterial cells than mammalian cells • Consist of a cell membrane, a cell wall and cytoplasm.

14. Bacteria • Classified by • Morphology • Size • Staining characteristics • Formation of spores • Nutrient requirements • Biochemical reactions • All are prokaryotes

15. Bacterial Morphology • Cocci (spherical) • Pairs--Diplococci • Chains--Streptococci • Clusters--Staphylococci • Rods, may be straight or slightly curved • Spiral shaped

16. Bacterial Staining Characteristics • Classified into Gram negative and Gram positive groups • Gram positive--dark blue/violet stain, due to a thick cell wall • Gram negative--red stain, due to a thin cell wall with high lipid content

17. Fungi • Many fungi in nature are beneficial • Used to make • bread • beer • wine • antibiotics • A few fungi are pathogenic • All are eukaryotes

18. Beneficial fungus • Saccharomyces cervisae

19. Fungi • Pathogenic species classified into • Superficial mycoses • Systemic mycoses

20. Superficial mycoses • Infect superficial tissues; skin, hair and nails. • Commonly called “ringworm” • See scaliness and alopecia (hairloss), sometimes redness

21. Systemic mycoses • Infect deep tissues; lung, bone, CNS, GI tract. • Often associated with certain geographic areas • Lower Sonoran desert--Coccidioides immitis • Central and southeastern US--Blastomyces spp.

22. Parasites • Large group of single cell (protozoans) and multi-cell (metazoans) animals which must coexist on another animal during some part of their life cycle • A parasite must also have the potential for causing disease in the host

23. Parasites • Websites of interest • Parasites and Parasitological Resources • http://www.biosci.ohio-state.edu/~parasite/home.html • Identification and Diagnosis of Parasites of Public Health Concern • http://www.dpd.cdc.gov/DPDx/Default.htm

24. Parasite Lifecycles • “If you know the enemy and know yourself, you need not fear the result of a hundred battles.” Sun-tzu, “The Art of War” • Knowing the life cycle of a parasite is the key to knowing how to prevent and treat infestation.

25. Parasite Lifecycles • Life cycles can be direct or indirect. • Direct--parasite eggs/larva can infect definitive host • Indirect--parasite needs to pass through an intermediate host prior to infecting the definitive host

26. Parasite Hosts • Definitive host--the species of animal responsible for housing the reproductive stage of the parasite • Intermediate host--the species of animal responsible for housing any of the non-reproductive stages of the parasite • Disease can occur in both types of host

27. Protozoan Parasite • Amoebas • Flagellates • Ciliates • Sporozoa

28. Toxoplasma gondii • A sporozoan parasite • Definitive host--cat • Intermediate host--almost any other mammal or bird • Causes self-limiting diarrhea in cats • May cause severe disease in immunosuppressed intermediate host

29. Toxoplasma gondii • Trophozoites in lung fluid from an HIV-infected person • Tissue cyst from a cat

30. T. gondii life cycle

31. Other protozoa • Giardia • Trypanosome

32. Metazoan Parasites • Trematodes--Flukes • Cestodes--Tapeworms • Nematodes • Arthropods--insects, ticks, mites

33. Cestodes--Tapeworms • Parasites which inhabit the GI tract of the definitive host • May cause lesions in many different tissues in the intermediate host • Do not have their own digestive system • Life cycle often indirect but may also be direct

34. Echinococcus granulosus

35. Tapeworm tissue cysts Cysts in a baboon heart

36. Hymenolepis (Rodentolepis) nana • A tapeworm of rodents and humans • Has a direct life cycle

37. Nematodes--The “Roundworms” • Worms that are round in cross-section • Body structure contains a GI tract as well as reproductive organs • Both direct and indirect life cycles • May live in many tissues in both the intermediate and definitive hosts

38. Ascarids • Common intestinal parasite of dogs, cats, swine and humans • Also called roundworms • Both direct and indirect life cycles • Infections in humans can result in visceral larval migrans or ocular larval migrans

39. Toxacara canis life cycle

40. Toxocara canis • Adults • Egg

41. Dirofilaria immitis Heartworm • A nematode parasite that lives in the right side of the heart in dogs and occasionally cats • Life cycle of this parasite requires passage through mosquitoes • Infection can cause heart failure

42. Heartworm life cycle

43. Acanthocephalans • Thorny headed worms • Seen in pigs and nonhuman primates

44. Arthropod parasites • Large group of external parasites that include • Insects • Ticks • Mites

45. Arthropod parasites • In lab animal science most likely to see • Mites • Lice • Fleas

46. Mites • Parasites in the arachnid family • Have eight legs in the adult stage • Live on the skin, sometimes deep in the hair follicle • May be zoonotic

47. Sarcoptic mange mite • Sarcoptes scabiei with multiple subspecies • Infest a multitude of species • Infestation is also called “scabies” • Can cause intense pruritis • Infestation is worse if animal is immunosuppressed

48. Sarcoptic mange in a dog

49. Scabies in a person

50. Prevention of Infectious Disease • In all cases it’s easier to prevent diseases than to treat them • Principles of prevention are simple and usually more cost-effective than treatment