Tiza writes:

The case presumably could be a space occupying lesion in immunocompromised patient, with history of keeping cats as pets most likely Toxoplasmosis.

Michele writes:

Hello TWIP team! Thank you for the fun parasite chat! It’s 84 degrees Fahrenheit which is warm even for California, in November. This gentleman presents with health concerns, complicated by HIV. His symptoms; lower limb weakness, fever, and  abnormal CT/MRI with edema.  His parasitic risks include living with a cat. Although there are no skin lesions like a scratch mentioned, he could have cat scratch fever transmitted from the scratch or bite of the cat or fleas infected with Bartonella henselae.  This is compatible with headache and one of the feline zoonotic diseases that does not cause any GI distress symptoms. It sounds like a course of antibiotics would be in order. I’m not sure if this can be identified by a blood culture but the history of a cat and Immune comprised condition are suspicious! 

Cheers to many more TWIP intrigues! 

Alexander writes:

Dear professors,

The patient with HIV/AIDS and ring enhancing lesions on brain MRI most likely has toxoplasmosis, which he may have contracted from the cat or possibly many years ago from raw meat. Differentials include neurocysticercosis and several non-parasitic entities including CNS lymphoma, metastasis, embolic abscesses, TBC and demyelination. 

Due to his HIV infection, the patient is at risk for most of them and needs antiretroviral treatment asap. Brain biopsy might be required to make the diagnosis, but you could empirically treat with sulfadiazine, pyrimethamine and leucovorin and monitor closely.

I hope you will get this email, I’ve already sent answers for the last two cases but they didn’t make it into the episodes. I hope I don’t send them too late. Thank you for the great case and all the best, 

Alexander from Vienna

Cam writes:

Hi TWiP Team,

Congratulations on episode 200, a great effort!

NSW, Australia, 21° C, 69° F, Partly cloudy

To cut a long diagnosis short. The intracellular protozoan parasite, Toxoplasmosis Gondii is my diagnosis. 


Show about parasitology, the most common answer is a parasite

The multiple mention of a possible source of infection (wife’s cat)

 CD4 < 100 via HIV, weak immune response to parasites

Ring Enhancing lesion, often seen due to T. Gondii infection

Many people with HIV/AIDS also have toxoplasmosis, due to recent infection or a previous infection that has reactivated

Blood tests to confirm the diagnosis should be done to check for the presence of antibodies to toxoplasmosis and or PCR testing to detect and measure T. gondii DNA in the blood or cerebrospinal fluid (CSF).

Treatment with Trimethoprim/sulfamethoxazole, (co-trimoxazole) and a plan to improve compliance with ART medications for the HIV. 

Dapsone and pyrimethamine are an alternative combination for treatment, again with improved compliance with HIV meds.



Wyatt writes:

Hello all,

This is Wyatt, MS2 now, in Loma Linda, and I am happy to have a spare moment to write again. I have been diligently listening from afar, and even gave a brief journal highlight on the article you all presented on the fungal killer of mosquitoes endowed with the venom of Australian spiders. I presented this to the Infectious Disease Interest Group here, and they loved it. Thanks for always recommending interesting reading. It has been great hearing from Dr. Naula as well, she is a great addition to the team!

HIV patients who are not taking their medications are unfortunately at risk for many awful complications. PCP pneumonia, Candidiasis, Progressive Multifocal Leukoencephalopathy (JC virus reactivation), and countless others. The fact that this is TWIP, and that it is affecting the brain with ring-enhancing lesions makes me automatically think toxoplasmosis encephalitis. This can present in many ways, but having focal neural findings is common. The tasteful addition of the family cat in the history was also helpful in the diagnosis. A Cysticercosis of Tenia solium would be in my differential as well. I might also consider a CNS Lymphoma, but there would not likely be as many lesions. I would also like to check out the coating on the man’s tongue, and maybe do a scraping to check for oral candidiasis.

To treat the toxoplasmosis, I would give pyrimethamine and sulfadiazine!

All the best from ever-sunny CA, thanks for all that you do,


Anthony writes:

Hello again! The lesions on the brain for this case study has me tied 50/50 between a progressed Balamuthia mandrillaris infection and a really really bad toxoplasma flare-up!

The mention of cats and HIV-1 leads me down the toxoplasma route – hopefully so as it is a ton easier to treat (bactrim and clindamycin) than a progressed Balamuthia infection!

– Anthony

Ken writes:

Dear TWIP team,

Greetings from Indianapolis in the Hoosier State! First and foremost, thank you all for your wonderful work and contributions. I consider myself a fairly new viewer/listener of TWIP, TWIV, TWIM, and Immune – I’ve started listening to your podcasts over the last year and have been addicted ever since. Excited to be writing in my first guess – I am a CPEP Clinical Microbiology Fellow and these case studies are a great exercise, learning tool, and alternative to my usual work commute carpool karaoke. 

On to the case: given the clinical presentation of our HIV-positive patient, CT & MRI results, his low CD4 count, and history of living with a cat. My guess is that this patient may be positive for Toxoplasma, possibly acquired from dealing with the cat’s faecal matter. I would also venture a guess that the “medicine” he had neglected to take may have included some form of prophylactic treatment. 

Look forward to hearing the answer to the case. Hope you all have a wonderful Christmas holiday!

Kind regards,


Kenneth Gavina, PhD
CPEP Medical and Public Health Microbiology Fellow “
Indiana University School of Medicine 

Scott writes:

Excellent TWiP 200. It was almost like you were starting a podcast on ecology. TWiECO has a nice ring to it. 

So this is my first go at a TWiP diagnosis, but I think Daniel gave even me enough clues to get this one. 

My diagnosis for the HIV-AIDS patient is toxoplasmosis. While the brain lesions could be caused by multiple bacterial or fungal infections, this being TWiP I went to toxoplasmosis. Toxoplasmosis is a common cause for brain lesions in AIDS patients. The Toxoplasma parasite probably came from the patient’s wife’s cat. Serological testing for anti-Toxoplasma antibodies should confirm diagnosis.

Steps going forward:

1. Treat the toxoplasmosis. The CDC website says patients can be treated with a combination of drugs such as pyrimethamine and sulfadiazine, plus folinic acid.

2. Encourage the patient to regularly take his anti-HIV medications. Find out what are the underlying causes of him missing doses. If it is truly just forgetfulness, maybe an app or person that regularly reminds him will help. Toxoplasmosis is one of many infections this man is at risk of contracting and dying from. He already appears to have a bad case of oral candidiasis, or thrush. A systemic infection from Candida or other fungus could be lethal. 

3. Tell the patient to avoid the cat’s litter box. There may be ways to limit Toxoplasma exposure from the cat by limiting where it goes and where it goes to the bathroom. Also, would treating the cat be useful?

Glad that most of the TWiP gang got together. Maybe in the not too distant future you can road TWiP to Glasgow.

Best Regards,

Madison, WI

Mats writes:

Dear all!

Sorry for the short answer! Headache + fever + CD4 below 100 and ringformed lesions in the brain sounds like cerebral toxoplasmosis. Serology might only yield pos IgG but PCR from CSF can give confirmation.

Non-parasitic dx include CMV, PML, cryptococcal meningitis and CNS lymphoma among others.

Thank you for a great show!

Best regards,