Dark Banquet

by Bill Schutt

  When an animal moves through high grass or brush, it causes physical disturbances to the environment as it tramples and displaces the soil and vegetation in its path. Ticks and chiggers take advantage of the vibrations produced during this process. Both show strong inclinations to climb upward—and the result is that they spend much of their hunting time perched at the tips of grass blades, sticks, and other objects located close to the ground. They also congregate along the outer margins of leaves belonging to weeds and other low-lying plants. When these substrates vibrate (owing to a physical disturbance like that produced by the movement of a nearby animal), both chiggers and ticks respond by lifting and waving their two front legs. This “questing” response increases the likelihood that the parasite’s legs (which bear an array of Velcro-like spikes, hooks, and bristles) will make contact with a potential host as it passes by. Once the initial contact occurs, ticks employ all eight of their legs (six in chiggers) to haul themselves onto the unsuspecting lunch wagon.*133

  Dr. Yeh pointed out a behavioral difference related to questing that seemed to spell even more trouble for those seeking to avoid encountering these parasites.

  “Around here, black-legged ticks generally quest in the early morning, when it’s not too hot and dry for them. Because Lone Star ticks prefer the heat, they quest in the afternoon. Unfortunately, that’s when they’re most likely to encounter people.”

  As far as speed goes, ticks are far slower than chiggers—slower moving, slower to bite, and slower to drop off after a bite. Additionally, unlike chiggers, which usually make a mad dash for your socks or belt line, once ticks have hitched a ride, they walk around the surface of their host’s body (often for hours) using thermal and chemical cues to search for a suitable feeding site.

  Some ticks, like those that prey on humans, aren’t particular about who or where they bite, while others are highly specific. For example, the larval instars of Rhipicephalus evertsi, a tick that preys on bovids (cows and their cud-chewing relatives), prefer the ears of their host while the adults of this species show a strong preference for attaching themselves around the anus.

  The cold tolerant tick Dermacentor albipictus thrives in the northern latitudes. In regions like western Canada, it’s responsible for Winter Tick disease in large ungulates like moose. These hoofed giants become so heavily infested with ticks (sometimes numbering nearly two thousand per individual) that they spend much of their time grooming themselves and incessantly rubbing against trees. The resulting hair loss (up to 80 percent in some cases) gives the stricken moose a gray or even white appearance instead of their normal dark brown color and has given rise to the term ghost moose. These animals are often emaciated from blood loss and exposure, and since their feeding behavior is severely disrupted, they also exhibit loss of stored body fat.

  Tick bites, and their behavior afterward, also vary significantly from what is seen in chiggers. After tilting their body (somewhere between a forty-five-and sixty-degree angle), ticks use larger versions of the chelicerae found in mites and chiggers to scissor their way into a host’s skin, where they embed themselves. Ticks also attach themselves to a feeding site with a rodlike structure called a hypostome. Unlike the chigger’s feeding tube (stylostome), the hypostome of the tick is an actual body part through which blood is drawn from the host. Backward-pointing, hooklike projections on the hypostome prevent the tick from being easily removed. Additionally, in many tick species, the salivary glands produce a substance that literally cements the parasite to its host until it finishes feeding. Larval and nymphal ticks (which are often confused with chiggers) have smaller mouthparts and their bites are not as deep as those of the adult (which can penetrate past the epidermal and dermal regions of the skin into the underlying hypodermis).

  Deeply embedded into their hosts, ticks breathe through an insectlike tracheal system, with the openings (also called spiracles) located on a section of the abdomen that remains above the surface of the host’s skin.*134

  As Dr. Yeh explained, there are a few unexpected positives related to the transition from black-legged to Lone Star ticks in the northeastern United States.

  “First of all, the bite of the Lone Star tick is more painful,” she said.

  “That’s always a big plus,” I remarked, my mind wrestling with that one as I scribbled down notes.

  “It makes them easier to detect,” Dr. Yeh continued, unfazed and exhibiting the patience that sometimes comes from working with the public.

  “Right,” I said, trying to figure out a selective advantage for a tick to have a more painful bite—there didn’t seem to be any.

  “Plus, STARI is milder than Lyme disease—although we don’t know a whole lot about it yet.”

  “Starry?” I asked, trying not to sound like a bat biologist investigating tick-borne diseases.

  “Southern tick associated rash illness. It’s caused by Borrelia lonestari, the bacterium transmitted by the Lone Star tick. STARI has similar symptoms to Lyme disease—fatigue, flulike stuff, and a rash.”

  “What makes it milder?”

  “It doesn’t appear to go chronic—no long-term effects like Lyme disease can have on the joints, nervous system, and heart.”

  “Is there a test to distinguish between Lyme and STARI yet?”

  The entomologist shook her head. “We haven’t got Lyme disease figured out yet—and now we’ve got STARI to deal with.”

  “Why do the symptoms of Lyme vary so much?” I asked.

  “If it isn’t treated early—and sometimes even if it is—many researchers believe that the flulike symptoms can give way to a menu of far more serious stuff later on.”*135

  “Is it tough to diagnose?”

  “That’s definitely one of the problems,” Dr. Yeh continued. “The blood test for Lyme disease is notoriously unreliable, and the disease mimics other maladies—arthritis and multiple sclerosis. And apparently there’s a latent form in which the bacteria that causes Lyme can hide in places like synovial fluid—where the host’s immune system can’t find it.”*136

  As I interviewed Dr. Yeh, a debate was raging in the media and elsewhere among physicians, infectious disease researchers, bloggers, and various mothers-against-ticks groups over the existence (or nonexistence) of a chronic form of Lyme disease. Contrary to what Dr. Yeh believed, a growing contingent of physicians and infectious disease researchers find no evidence of a relationship between Lyme disease and long-term health effects. These professionals base their stance on recent studies that showed no trace of Borrelia in the spinal fluid, blood, and urine of well-documented Lyme disease patients who were acutely treated with antibiotics but complained of lingering symptoms months later.†137 Similarly, Dr. Lauren Krupp and her colleagues at Stony Brook University found that treatment of patients with long-term antibiotics produced results no better than with the placebo.

  Those who opposed the concept of chronic Lyme disease offered several explanations for why patients previously treated for the disease showed serious health problems months and even years later. Supporters of the postinfection syndrome hypothesis proposed that Borrelia burgdorferi triggers neurological and other long-term problems in some Lyme disease patients before being wiped out by an acute course of antibiotics. Alternatively, some researchers felt that chronic Lyme disease patients who tested negative for Lyme disease, or who had false positives, may never have had Lyme disease to begin with but were simply misdiagnosed.

  The debate about chronic Lyme disease is still very much alive and there is abundant information out there from both sides of the fence.

  I asked Dr. Yeh to clarify her position. “Do you think there are different strains of the pathogen?”

  “There’s every indication,” she said. “It’s one of the things that makes testing for Lyme disease so difficult. Too many false negatives.”

  I later learned that previous vaccination against Lyme disease, or prior treatment for syphilis or dental infections, could cause false positives by triggerin
g an antibody response.

  Suddenly, the withdrawal of the Lyme disease vaccine began to make sense.

  “Is that what happened with Lymerix?” I asked.*138

  “That’s one reason they stopped making it,” Dr. Yeh responded. “The vaccine was designed to target a specific outer surface protein in Borrelia burgdorferi, but changes in those proteins have produced different bacterial strains. As a result, the vaccine was never all that effective to begin with—something like 40 percent. Add that to the fact that it was always a niche market, with maybe ten thousand doses in the entire United States. And then there was the big controversy a few years ago about vaccinations of all kinds. Should we give them? Are they safe?”†139

  “And it’s not like vaccines are the big moneymakers,” I chimed in, and Dr. Yeh nodded.

  Just as my interview with her was coming to a close, Dr. Yeh said something that sent a chill down my back. “Yeah, well, that moneymaking thing might change pretty quickly if bird flu ever evolves into something humans can pass off to each other.”

  And at that point, I realized that there was nothing left to say.

  Very small, but solely preoccupied with doing harm.

  —Paul Le Cointe

  9.

  CANDIRU

  with a Capital C and That Rhymes with P

  Several years ago I was involved in teaching a course at Long Island University that took twenty undergrads on a riverboat excursion up the Brazilian Amazon. We’d been in Manaus for three days, having spent the previous week at a rough-hewn research station called Kilometer 41,*140 and by the time we pulled into Manaus, we were all ready for a dose of civilization. The city was hot and crowded, but the food (and beer) were wonderful and the open-air markets were fascinating—the bounty of the Amazon River on display in all its unrefrigerated glory. On the afternoon of our third day in Manaus, we checked out of our hotel and hauled our gear and belongings down to the harbor. There were boats of every size and shape lined up for what seemed likes miles, and I was reminded of the activity around a particularly busy anthill. Cargo was unloaded (all of it by hand) and replaced by throngs of people (all of whom seemed to be having a pretty good time). Fruit, fish, and vegetables of every size and shape were carried up a steep set of stairs that led to the city and its markets. Finally, we located the boat that was to be our home for two weeks. Gleaming white against the muddy and polluted water, the Victoria Amazonica was an eighty-foot riverboat with fourteen private cabins (each with showers and AC). In other words: we would no longer be roughing it.

  Our captain was Moacir Fortes, the renowned Amazon guide. Mo was high octane, sharp as a stingray barb, and funnier than hell. After boarding the Victoria Amazonica, we stowed our gear and headed for a large centrally located room that would become a combination dining room/meeting place and indoor lounge. Captain Mo arrived shortly thereafter to address the group. He began by going through his famous list of “the seven perils of the Amazon River.”

  “There are thousands of creatures in the river that we enjoy—but only seven that enjoy us.”

  It was all very humorous as Captain Mo counted off some well-known local denizens—piranhas, stingrays, electric eels, anacondas, and black caiman (a South American cousin of the alligator). There was even a giant catfish, called the piraíba, that could swallow a person whole.

  Finally, Captain Mo began describing a creature I hadn’t heard of before. He was two sentences into his spiel when I noticed that the laughter in the room had stopped. In fact, the entire room had gone quiet.

  The silence was broken several seconds later by the distinctive alarm call of a young North American woman: “It swims up your what?”

  I was suddenly confused and I leaned in toward my friend, filmmaker Bob Adamo.

  Bob was wearing a pained expression. He was also bent forward in his chair, as if he’d been punched in the gut.

  “Did I just friggin’ hear that?” I whispered.

  “I hate it when fish swim up my Telegraph Office,” came Bob’s strained reply.

  I had heard Mo correctly.

  By 2006, as I began planning a return trip to the Brazilian Amazon, I had already learned quite a bit more about the candiru (or carnero), the creature whose very mention had caused such a commotion aboard the Victoria Amazonica five years earlier. I also knew that “Telegraph Office” was Captain Mo’s unique way of referring to either human genitalia or the terminal opening of the digestive tract. In the case of the candiru, the term had been used because of the fish’s legendary penchant for swimming up the human urethral opening and lodging itself there.

  There was no shortage of candiru-related horror stories either, to the point where many sources claimed that it was even more feared by locals than its higher-profile river-mate, the piranha.*141 According to some of these authors, coconut shells, pudendal coverings made of dried palm leaves or bark, and wicker baskets (which might have served double duty on trips to the market) were worn to protect the external genitalia from candiru attacks.*142 But even these simple devices could be considered advanced anticandiru technology compared to the technique first described by early-nineteenth-century explorers Carl Friedrich von Martius and Johann Baptiste von Spix:

  These fishes are greatly attracted by the odor of urine. For this reason, those who dwell along the Amazon, when about to enter the stream, whose bays abound with this pest, tie a cord tightly around the prepuce and refrain from urinating.

  Fortunately, as with the candiru’s fellow sanguivore, the leech, there’s a reliable and fairly comprehensive reference to this piscine vampire. In Candiru: Life and Legend of the Bloodsucking Catfishes, Stephen Spotte explores the bizarre world of these nasty creatures. Thankfully, the whole thing is done with clarity and some comic flair (i.e., it is not a textbook) and there’s a nice chunk of science in it as well.†143

  Candiru belong to the Trichomycteridae, a family consisting of about two hundred species of “small to very small, slender-bodied freshwater catfish.” Trichomycterids, most of which are rather plain-looking insect eaters, belong to the much larger group, the order Siluriformes (catfish), which consists of thirty-five families and around three thousand species. The catfish, in turn, fall under the incredibly broad heading of ray-finned fishes (Actinopterygii), as do most fish you can name with the exception of sharks, skates, and rays.

  Within the Trichomycteridae is a small subfamily, Vandelliinae, which currently contains six genera of obligate blood feeders inhabiting the Amazon and Orinoco rivers of South America. These vandelliines are commonly referred to as candiru (which Spotte pronounces “candy-roo”). According to Dr. Spotte, “Formal descriptions of candirus have been published since 1846, but the question of how many species exist has no clear answer.” While some researchers think it’s likely to be somewhere around fifteen (half of them belonging to the genus Vandellia), Spotte believes there could be far fewer. “Many species have been named on the basis of one specimen, and without the ability to measure variation within that species, it’s impossible to determine if there’s overlap with other supposed species.”*144

  Physically, candirus are nowhere near as nasty looking as a decent-sized piranha. They are eel-like in appearance with their dorsal, anal, and pelvic fins set far back on their translucent bodies, close to the tail. Their small eyes are located near the top of their dorsoventrally flattened skulls. Candirus have tiny sensory barbells (unlike the prominent whiskerlike structures found in many catfishes), and they lack the stout and often dangerous dorsal and pectoral spines that have punctured countless anglers.

  Although most people would consider this a good thing, the chances of ever seeing a candiru in the wild are quite low—that is, of course, unless you regularly fish the Amazon River and its tributaries with a cow lung tied to a piece of rope (a technique detailed in an article published by Kenneth Vinton and W. H. Strickler in 1941). The tiny fish usually remain hidden in the sand, mud, or leaf litter. They’re also found in shallow, fast-moving wat
er. This secretive lifestyle (which we’ve seen in other vampires) appears to be one of the reasons why studies on topics like the candiru’s reproductive biology as well as many other aspects of its behavior remain sketchy or nonexistent.

  Vendellia cirrhossa is probably the best-known species of candiru, although Vendellia wieneri has the coolest name. Candiru (which typically range from one to six inches in length) prey on larger fish and they feed by wiggling under their hosts’ gill covers (opercula), the flaplike structures that shield the gill chambers. These opercula open and close as the fish breathes, and once inside, the tiny vampires secure themselves to the delicate gill lamellae (which are arranged like pages in a book) by a series of tiny, backward-facing hooks. These integumentary teeth or odontodes (sometimes called denticles) are found in patches around the candiru’s head (including their own gill-covering opercular and interopercular bones). Once secured, the candiru utilize two or more rows of needlelike teeth to bite through one of the blood vessels that function in gas exchange between the feathery, high surface area gills and the fish’s body.*145 Apparently, muscles in the candiru’s mouth and pharynx pump the blood into the digestive tract.†146

  The candiru feeds for somewhere between thirty seconds and nearly three minutes, the blood clearly visible through its engorged, nearly transparent body. Since they sometimes feed in groups, the blood loss and damage to the host’s gills can be considerable as pieces of shredded gill lamellae are sliced off by the teeth and rasped off by the odontodes.

  Do candirus ever swim up the human urethra? Apparently, it does happen, although thankfully, occurrences are extremely rare. There have been numerous anecdotal descriptions, reviewed in depth by Spotte, but the first confirmed attack was reported by Drs. Spotte, Paulo Petry, and Anoar Samad at the 2001 meeting of the American Society of Herpetologists and Ichthyologists. Dr. Samad, a urologist, had treated a young man who showed up several days after a swim in the Amazon during which he had decided to remove his swim trunks before urinating.