Monday, May 23, 2016
ZOONOTIC TALES: LIVING WITH ROACHES
by Genese Sodikoff
There is the nightmare of fecundity and the nightmare of the multitude. There is the nightmare of uncontrolled bodies and the nightmare of inside our bodies and all over our bodies. There is the nightmare of unguarded orifices and the nightmare of vulnerable places. There is the nightmare of foreign bodies in our bloodstream and the nightmare of foreign bodies in our ears and our eyes and under the surface of our skin.
—Hugh Raffles, Insectopedia
I am writing anthropological stories of zoonosis, disease that spills over from animals to humans and then potentially spreads person-to-person. A zoonosis may erupt into an alarming epidemic (Ebola, HIV/AIDS), or may idle in a reservoir host as an ever-present threat (rabies, Lyme disease, hantavirus). Insects often vector these diseases by sucking up the tainted blood of an animal and injecting it into human skin. Zoonosis can encompass parasitic infections too, such as when larvae afloat in the drinking water or nestled in the litter box penetrate our bodies and mature into worms that make us sick. By some definitions, zoonosis and vector-borne diseases are distinct categories, even though viruses and bacteria introduced by insects into human populations may have originally been lifted from an animal.
Beyond the role of vector, there's another kind of insect that acts more as a disease server. It wears pathogens like foundation, coated with bacteria, viruses, fungi, and larval cysts, as it goes about its business. Chief among these is the cockroach, whose glossy cuticle teams with unwholesome microbes. Since the cockroach does not convey pathogens from vertebrate animals to humans, it does not transmit zoonotic disease, properly understood. Instead it traffics pathogens that are just out there, free floating in the dwellings and detritus of humanity, and deposits them on our food and our wounds. Cockroaches are responsible for introducing Staphylococcus into hospitals and spreading antibiotic resistance bacteria. They sprinkle kitchen counters and cabinets with Salmonella, Shigella, and E. coli. They truck Hepatitis A from sewers into homes. If that isn't enough, their odiferous droppings and sloughed-off skins trigger asthma attacks. The list goes on.
Several centuries ago, the ancient insect order, Blattodea, embedded itself in our history as we began voyaging overseas. Periplaneta ("around the planet") is the genus to which several pest species belong. Drawn to our dwellings and slop, cockroaches became our shadow society: well fed, enamored of our stuff, and habituated to the dark, moist spaces we create. We, in turn, have adapted to urban life with cockroaches in various ways, none of them evolutionarily positive other than being self-defensive. By laying sticky traps and poison pellets and carrying out insecticidal spray regimes, we keep roaches at bay. Mostly we have learned to push them into the dark crevices of our consciousness as much as possible because they are legion, and they are disgusting.
Yet also fascinating, as I have been learning from my colleague and friend Jessica Ware, evolutionary entomologist at Rutgers University, Newark, who was part of the team that recently identified a new invasive species, the Japanese cockroach (Periplaneta japonica), in Manhattan. Certain roaches, says Dr. Ware, have developed cunning responses to getting stomped on. Cockroaches carry their eggs in an ootheca, a kind of "suitcase with a hinge," which some females can release from their bodies upon being smushed, leaving hundreds of larval progeny to mature on their own. When ready to hatch, the baby roaches heave a collective breath, pop open the hinge, and stream out.
Although we equate them with filth and disease, says Rutgers University-Newark doctoral student Xueyang ("Sean") Fan, cockroaches are themselves fastidious creatures, obsessively grooming their antennae—their sensory organs—by swiping them through their mouths. Another fact: if a cockroach loses its head, it can live for about a month breathing through spiracles on its body segments, finally dying from hunger and thirst.
Cockroaches (from the Spanish, cucaracha, "crazy bug") probably arrived in the Americas on slave ships, Dr. Ware tells me. The theory is that the American cockroach (Periplaneta americana) sailed the triangular trade route of slavery, embarking on ships in West Africa, and settling in the Americas and Europe by around 1625.
I have seen the old drawings of slave ships that crossed the Atlantic, of tortured African bodies crammed horizontally onto lower decks like sardines, or else sitting upright and wedged between each other's legs. These were the packing strategies slavers used to hedge their bets on how much human chattel would survive the Middle Passage. Millions died. Imagine now, in more specific detail, the captives lying there, starving, for weeks at sea on fouled floorboards shared with swarms of cockroaches that sipped any moisture from their parched mouths, nibbled their toenails as they slept, and ferried bacteria from body to body, ensuring an endless cycle of gastroenteritis ("the flux") amongst them.
Waves of immigrant cockroaches arrived in the Americas and scattered into gradually emerging cityscapes. Through time, they have established genetically distinct enclaves in buildings that are nested within ethnically subdivided cities. All these formations are constantly in flux as bodies migrate. Roaches colonize new territory whenever they crawl into a handbag or get packed up in boxes with our possessions.
Cockroaches in hospitals pose a serious problem. They circulate pathogens around stitched-up cuts and open wounds, wreaking havoc on the healing process. The pathogen load of German cockroaches extracted from US hospitals was found to carry bacteria types that cause wound infections, diarrhea, food poisoning, conjunctivitis, gas gangrene, leprosy, sepsis, typhoid, skin and organ infections, and pneumonia. The problem has worsened with the rise of antibiotic resistant bacteria, like MRSA, which do not harm cockroaches in the least but kill approximately 50,000 people per year in the US.
Urban roaches have the upper hand in our skewed symbiotic relationship. But out in the wild, cockroaches are very different creatures. Entomologists at Rutgers University, New Brunswick keep bins of cockroaches in darkened rooms of the Department's basement. Wlodek Lapkiewicz has an assortment of exotic roaches from other continents. Unlike the domestic varieties, the exotic cockroaches carry no pathogen load, living as they do in unsettled spaces: the Australian outback, South American caves, and tropical rain forests. They are "clean." Some are kept as household pets, and others make good food for other pets. A few species, like the giant burrowing cockroach of Australia, take several years to mature and reproduce (unlike the more fecund distant cousins). These can fetch prices of $100 or more per insect.
The exotics vary widely in appearance. The slight banana roach is grasshopper green. The tan "peppered roach" has speckles of dark brown. The brown Dubia roaches, popular feeders for reptiles, "don't stink," Wlodek says appreciatively. (Cockroach colonies otherwise give off a musky, fungal smell, the telltale clue that your place is infested.) The Giant cockroach, Blaberus giganteus, native to Central and South America, has a wingspan of up to 6 inches across. The black "Question Mark" roach sports gold punctuation marks on its back. The "Domino" roach's name speaks for itself. An evil jack-o-lantern grins on thorax of the "Death Head" roach. The "Halloween" roach resembles a broach, banded in gold, orange, and black. TheLucihormetica luckae glows in the dark if it eats the bioluminescent flor de coco mushroom of Brazil, making it look to predators like a toxic click beetle and to humans like a tiny, gleaming-eyed alien.
There is nothing remotely beautiful about the common American, German, and brown-banded cockroaches. Even though most of us can't identify the subspecies, we know a roach when we see it. The entomologists at Rutgers are working diligently to control urban roach populations. Chen Zha, a doctoral student working under Dr. Changlu Wang, traps live roaches in apartment units and nursing homes (restaurant owners do not, as a rule, choose to participate in these studies) and brings the live specimens back to the lab, where they are placed in bins and fed peanut butter and jelly. "They eat better than I do!" said one masked grad student as he rearranged the bin habitat with a pair of tweezers. The masks protect the scientists from inhaling an excessive amount of roach allergens. Chen traces how many roach generations it takes for insecticide-resistance to evolve and concocts the most effective chemical brews to keep them in check.
Meanwhile, on the Rutgers-Newark campus, Sean Fan, who works under Dr. Ware, sets sticky traps for his research on cockroach genetics. Sticky traps kill the roaches, but Sean only needs their DNA. The genes reveal the effects of a group's habitat, be it the lunchroom of a university office or a nearby store, as well as the degree of inbreeding going on. The quality of the roach's diet and the level of insecticide soaked up by the living space are reflected in the genes, as is the pathogen load the insect carries. Sean sorts roach genes from bacteria after pulling off the roach's leg and submerging in a solution that makes the cells explode. "The DNA flows of the open end of the leg (which used to be attached to the body) and into the solution," Dr. Ware explains. Good pathogens can also be had on the roaches' wing surfaces and in their guts.
Although cockroaches are immune to the bacteria that sicken humans, they do suffer from other ailments, such as fungus and mites. Certain bacteria have co-evolved with roaches as "endosymbionts," living inside their body fat and colorless bloodstream and enabling roaches to sequester and store nitrogen, which they need for growth, from even the scrappiest of diets (roaches can survive on meals of feces and Styrofoam).
If urban roaches have any redemptive value for us, it lies in their resistance to superbugs. The rise in multidrug-resistant bacterial strains challenges scientists to ferret out new sources of antibiotics in nature, which, unlike synthetic drugs, have nuanced properties that make them more effective. Where better to look than at insects crawling around the pathogenic stew of hospital surfaces? A few years ago, scientists discovered antimicrobial activity in cockroach brain tissue, which explains their resilience to unsavory environments. The cockroach brain contains a rich vein of antibiotics. We just need to figure out how to mine it.
This is life in the late Anthropocene, the age of human dominance on the planet, an age of blighted landscapes, warming temperatures, mass extinction, overcrowded cities, zoonotic pandemics, superbugs, nuclear fallout, and mind-boggling advances in biotechnology. The irony, that a creature that flourishes in our waste and toxic residues, one that has come to symbolize life in a post-apocalyptic, peopleless landscape—the Cockroach, the Survivor—may well prolong our lives a while longer.
Posted by Genese Sodikoff at 12:40 AM | Permalink