NP4E Flashcards
Bacterial infection elicits a _________________response that triggers the edema cycle, and we have examples of thromboembolic disease that causes infarction.
suppurative inflammatory
__________ causes neurological dysfunction through direct effects on the target cell, although indirect effects were evident when impacting vasculature or triggering deleterious host immune responses.
Virus infection
Viral infection may trigger autoimmunity resulting in ___________
primary demyelination
Fungi can switch between two life styles:
- sexual replication in the mycelial form
- asexual replication as yeast
Temperature and available nutrients will determine the approach
Refer to infections caused by organisms in the following genera: Blastomyces, Coccidioides, Histoplasma, and Cryptococcus.
Systemic mycose
Fungal infection in the mycelial form is often restricted to those with compromised immune function because the branching arms of these organisms trigger a robust inflammatory/immune response. For this reason, we refer to these as ____________
opportunistic infections
The route of entry is commonly the lungs, where organisms penetrate blood vessels to cause vasculitis, and emboli break off, some of which land in the brain to cause infarcts.
opportunistic infections
If the infarcts are small and the animal survives the initial insult, we will see a _____________________ inflammatory response, resulting in a mass lesion.
granulomatous or pyogranulomatous
When yeast lodge in tissue, they cause a_________________ inflammatory response.
granulomatous or pyogranulomatous
(systemic mycosis) Blastomyces dermatitidis => _________
granulomatous encephalitis
The example of a dog shows multifocal granulomas, and histology showed that these granulomas contained large yeast with prominent capsules, consistent with _____________ . Budding could be seen, indicative of asexual replication.
Blastomyces dermatitidis
________________ is unique in that the yeast capsule does not elicit a strong host inflammatory response, and it resists phagocytosis by macrophages.
Cryptococcus neoformans (systemic mycoses)
The illustration of a cat shows a nasal cavity filled with the organism, extending over the soft palate, and invading the brain through the cribriform plate. Death is caused by the:
mass of organisms causing meningitis, disruption of CSF resorption, and triggering of the edema cycle
opportunistic fungal infection => ______________
pyogranulomatous encephalitis ( inflammatory response to a fungal organism with pigmented hyphae)
There is a class of parasites in the Toxoplasma, Neosporum, and Sarcocystis genera that adopt the following lifestyle:
- sexual replication in the gut of a carnivore or omnivore
- shedding of oocytes that contain many infectious particles in the feces
- Oocytes are consumed by an herbivore, releasing tachyzoites that penetrate the gut lining and enter the vasculature
- transports the tachyzoites to muscle, where they exit and replicate within cysts as bradyzoites
- definitive host then consumes muscle of the intermediate host, together with the tissue cysts, and now they are infected, with sexual replication in the gut
There is a class of Protozoan parasites:
- Toxoplasma
- Neosporum
- Sarcocystis
The definitive and intermediate hosts are specific to the protozoan:
Toxoplasma gondii
Definitive Host = cat
Intermediate Host = rodent
The definitive and intermediate hosts are specific to the protozoan:
Neosporum caninum
Definitive Host = dog
Intermediate Host = cattle
The definitive and intermediate hosts are specific to the protozoan:
Sarcocystis neurona
Definitive Host = opossum
Intermediate Host = raccon
The problem occurs when we don’t have the right intermediate host. Tachyzoites get lost during vascular dissemination. Some land in the brain where they may bludgeon their way through vascular walls and incite a tremendous _______________ response. Sometimes it is the definitive host that is the atypical intermediate, and this may be associated with a degree of immune suppression
non-suppurative inflammatory
It is common in rabbits (80% in the US). This protozoan is in a different phylum from those we just discussed. Rabbits are the definitive host with direct rabbit-to-rabbit transmission through urine. Ingestion of spores results in vascular dissemination of the protozoa to multiple organs, particularly the kidney, where replication results in urinary shedding. But that means that organisms can also find their way into the brain, where they cause granulomas that are only visible by light microscopy.
Encephalitozoon cuniculi
There are no gross lesions. The organisms are very small (they are obligate intracellular parasites), requiring special stains to visualize. These granulomas are clinically incidental, which makes sense given that rabbits are the definitive hosts.
Encephalitozoon cuniculi
(true/false) Not all lesions are significant. If you are working up a case of a rabbit with a severe head tilt and you see these lesions on histology, blame the head tilt on Encephalitozoon
false
protozoal myeloencephalitis vs herpesvirus myeloencephalitis
Parasitic migration (larval migrans):
(a roundworm of raccoons) causing larval migrans in children or dogs
Baylisascaris
Parasitic migration (larval migrans):
Is a tapeworm in the intestine of cats. Eggs are shed in the feces, and when those are consumed by rodents, emerge as larvae that form tissue cysts in organs that a cat is likely to eat (e.g., muscle).
Taenia taeniformis
Taenia taeniformis: The larvae get lost, ending up in locations that may include the central nervous system where they form cysts. These cysts have been given the name:
Cysticercus fasciolaris (slowly growing mass lesion that will stop growing at some point, and they do not elicit an inflammatory response)
The real problem happens if one of the cysticercus structures ruptures – that’s when the __________ happens.
inflammation
Parasitic migration (larval migrans):
Larvae get lost, and in the case illustrated here they ended up in the subarachnoid space. The problem is that they may sometimes stimulate a vascular hypersensitivity response resulting in a massive arteriospasm, resulting in cerebral infarction. The latter has been given the descriptive name “feline ischemic encephalopathy”
Cuterebra in a cat (right host, wrong location)
Parasitic migration (larval migrans):
This is a parasite of white-tailed deer and when it enters the wrong host (moose or camelids) migrates in nervous tissue.
Parelaphostrongylus
Here is the crazy life cycle:
- Second and third-stage larvae reside in snails and slugs that are ingested by deer and release larvae that migrate to the dura, where they mature into adults.
- Adults lay eggs that hatch into the first stage larva and this larva migrate to the lungs via the bloodstream.
- From there, they migrate up the airways into the oropharynx, are swallowed, and are then passed into the feces where they may be ingested by snails and slugs to mature into second and third-stage larvae.
Parelaphostrongylus in a llama (wrong definitive host)
Parelaphostrongylus tenuis =>
meningeal worm
