Noah writes:

We know Dr. Despommier is getting on in years, so in light of him missing the most recent TWiP, please update us on Twitter or the appropriate medium so we know that he is alright.

Wink writes:

Dear TWIP team,

As a child of Queens, I would like to offer a different perspective on the case from the “outer boroughs.” NYC makes a partial ring around Manhattan that you might think of the tiara of New York, with the jewels in Queens. The empty part tiara falls on New Jersey, so you could think of it as a void. Another way to look at it is that Manhattan is in the center of New York’s corpus, making it the bowels of New York. Regardless of where this worm was acquired, my wild guess is a Dirofilaria species. I think D. immitis and repens are occasionally found in the conjunctiva and they are on the right order of length (if I did the math right). I am not at all confident about my guess, but it’s the best a poor boy from Queens can do.

The formerly terse Wink Weinberg

Mike in Oregon writes:

Hi guys

I’m guessing the woman picked up Baylisascaris procyonis after chasing the raccoons out of her attic.

Mike in Oregon

Alan writes:

Dear wise TWIPwalas,

Weather in Kona: 33ºC/91ºF, Humidity 88%. Has been an unusually rainy week.

Here’s my guess for the the Brooklyn patient with a motile ocular worm.

It definitely sounds like an Ocular Larva Migrans (OLM), but caused by what?

Toxocara canis (T. canis) or T. cati is the most common cause of typical OLM

Baylisascaris procyonis causes a more severe and chronic form but because of the larger size of the larvae coupled with their ability to grow inside different organs causes more damage.

Ancylostoma caninum, Strongyloides stercoralis and Ascaris lumbricoides can also rarely make it to the retina, but they are all larger than 1850um and I pretty sure would have cause much more noticeable signs and symptoms.

Using a little indirect ophthalmoscope, you would be pretty good to see it at all, but in reading today, the new Scanning Laser Ophthalmoscope (SLO) with the blue wavelength, reportedly produces a high contrast background to better check for worms which show up white on the fundal exam.

Your serology came back negative for Toxocara canis, but it is famously negative, showing positive for only perhaps 45% of cases, so that is still my guess, but the ELISA for Toxocara available from the CDC is reportedly much more sensitive.

If you have a laser, you can usually kill it directly with photocoagulation, and then reduce the inflammation with steroids, but without access to one, for a motile worm, you are left with the difficult choice of needing to use antihelmenthics (albendazole) without causing catastrophic inflammation.  Interested in your treatment and outcome.

Dickson, we missed you last week!

But thanks to everyone for investing your time in such a wonderful series of podcasts.

Allan Robbins

Kona Hawaii

Iosif writes:

Dear Twip Team,

I would guess that our patient has DUSN (Diffuse Unilateral Subacute Neuroretinitis) as a result of Ocular larva migrans. This condition can be caused by a reaction to a worm that unfortunately has somehow made it’s way into the eye. Looking up the parasitical causes leads to a variety of different offending organisms.

Going one by one:

1) Brugia malayi or Wucheria brancrofti – Both are more endemic to India and other areas and I would not expect to find them in the US without a travel history.

2) Baylisascaris procyonis – No history of contact with raccoons or raccoon feces, but possible. They are usually about 1500-2000 um, so the size matches well.

3) Toxocara canis – Could easily have exposure to a dog or their feces. The adult worms are usually much larger though (9-18cm rather than 1.85cm).

4) Gnathostoma spinigerum – Usually obtained from raw or undercooked meat eaten in India. Unlikely.

5) Strongyloides stercoralis – Usually obtained from a more tropical environment although she could have obtained it from the stools of someone else. Adult size around 1.5mm and so could meet criteria.

Overall I would say my most likely diagnosis is either Balisascaris procyonis or Strongyloides and would ask further questions about risk factors such as raccoon exposure.


Iosif Davidov

Dave writes:

Good Doctors

Here is picture of the tick removal card I promised long ago. I got this from some Swiss folks I shear for near Kelowna BC. This year we took 25 ticks off one of their alpacas, 15 off another and 10 off the third one.  In my experience this is the simplest and most effective way to remove ticks and it stores in your wallet. All you have to do is line the slit in the card up with the tick’s head and slide it forward on the skin until the tick is in the slit, then gently lift the card and it pulls the tick out of the skin. You can easily check to make sure you have all of the tick. Don’t forget to carry a couple of zip lock bags so you can keep the tick and send it in to have it checked for Lyme.


I haven’t found a place to buy them in Canada but I’m sure you could buy them online.

Thanks again for your wonderfully informative podcast.

Shearer Dave From smoky southern Alberta where it’s 32c with a light breeze. A beautiful midsummer afternoon.

Adam writes:

Dear TWiP crew,

In the most recent episode, it was stated that there is no such thing as a sterile body fluid. The crew mentions that PCR-based methods have been used to detect bacterial DNA in basically all fluids tested to date. In the past, culture-based methods seemed to indicate that certain fluids, such as urine, did not contain any microbes.

Is it known if the presence of bacterial DNA in a sample means that an intact, replication-competent bacterial cell is also present? Could the positive PCR result simply be due to the presence of genomic fragments from dead bacterial cells that are being filtered or passing through that particular body fluid being sampled?

This brings to mind an arc on TWiV. The TWiV crew regularly talks about papers where they find a sample to be positive by PCR for a particular virus but then the hosts want to know if any virus can actually be cultured (or “plaqued”) out of that sample.

Please provide some insight if you have any on this apparent dichotomy. Thanks and keep up your great work. I thoroughly enjoy your podcasts and even use them as an aid to teach undergraduates about the wonders of the microbial world!

Best wishes,


Adam writes:

Dear TWiPsters,

Long time listener, third time emailer.  This week while looking over some tomato plants in the family garden, my father discovered some rather disturbing parasites that might be of interest to TWiP.  For several years we’ve had hornworms munching away at our tomato plants, but it seems this year nature helped us get our revenge.  Included below are some photographs my father took of what appear to be wasp larva covering most of an adult caterpillar.  The caterpillar was a bit sluggish but clearly still alive.
While I was aware of parasitic wasps from both TWiP and TWEvo, my father knew about them from borrowing my copy of Parasite Rex by Carl Zimmer.  I assume this book has already been a pick of the week but if not feel free to include it as a listener pick.



(You’re welcome to use or share those images as you see fit, although a quick Google search reveals there’s no shortage of hornworm/wasp photographs.)

Anthony writes:

In the past are the days when one might only encounter raccoons in the greener areas of Staten Island or the fringes of the Bronx.  Now they are in Manhattan, too:

And for Baylisascaris, it’s not the raccoons themselves but the droppings that are the worry.  Latrines may be on fire escapes or roofs.   With rain, egg laden water can splash on those below without any warning of a hazard.

Here in Jersey City, I no longer can put out the plastic fish pond in the summer.  Dealing with the midnight bathers is just too much trouble.  I work with volunteers who set up feeding stations for outdoor cats.  Food now can only be offered during the daylight hours.  When it’s dark, crowds of of raccoons chase the cats and eat everything.  

Raccoon Roundworms — The Hidden Horror


Anthony writes:

Guardian — Hookworm, a disease of extreme poverty, is thriving in the US south. Why?

Exclusive: in America, the world’s richest country, hookworm, a parasitic disease found in areas of extreme poverty, is rampant, the first study of its kind in modern times shows

by Ed Pilkington in Lowndes County, Alabama

Tuesday 5 September 2017 11.53 EDT Last modified on Wednesday 6 September 2017 17.00 EDT

Children playing feet away from open pools of raw sewage; drinking water pumped beside cracked pipes of untreated waste; human faeces flushed back into kitchen sinks and bathtubs whenever the rains come; people testing positive for hookworm, an intestinal parasite that thrives on extreme poverty.