BLOODSUCKERS
It is perhaps one of the supreme ironies that humans created their shelters not just to escape the weather, but also to get away from hungry carnivores, only to find that
they had created the perfect microhabitats for a new band of secret microcarnivores – the bloodsuckers. Blood had been sucked before, often enough – mosquitoes, midges, ticks and
leeches were but a few of the many attackers to have targeted humans and prehumans long before caves or bivouacs had been contemplated. But the false sense of security imparted by the sacred
space has opened up humans to even more frustrating attack.
Human blood (indeed all mammalian and avian blood) is a useful high-protein nutrient; it is conveniently liquidised for easy consumption, uniform in
consistency and biochemical make-up for easy digestion, and readily discoverable by virtue of the copious animal scents and smells given off by its owners. It is no surprise that bloodsucking has
evolved on more than 20 separate occasions in insects, and also in ticks, leeches and vampire bats (Lehane 2005). Nevertheless, this is quite some achievement, because drinking blood is not just a
passive puncturing and lapping up; it is inserting a delicate hypodermic needle and having to prevent the very capable anti-bleeding effects of the host’s clotting mechanisms from immediately
blocking up the attacker’s mouthparts.
Human blood clotting is a complex business, but because it is so important in medicine it is rather well understood. Briefly, damage to the capillary blood vessels exposes a ‘tissue
factor’, which activates tiny circulating blood cells called platelets. The platelets bind to the underlying tissue of the damaged area, changing shape as they do so from smooth spheres to
long-tendrilled mop-heads, and creating a tangled primary plug. Meanwhile circulating ‘clotting factor’ proteins bind to the platelets to strengthen the clot. It’s all very
biochemical bricks and mortar, but there are countless different chemicals involved in a veritable physiological cascade. It all happens in milliseconds, and it is very effective, otherwise
we’d quickly bleed to death every time we nicked ourselves shaving or slipped with the bread knife.
In order to take a swig of human blood an attacker initially has to locally disable the clotting system, and this always involves injecting anticoagulant chemicals of its own first, before it
can take down its bloody draught. It is the human body’s immune response to these alien proteins that causes the allergic reaction of the itchy spot, and in some people a more ferocious
reaction causes a swollen bite mark as big as a hen’s egg. This is annoying enough at the time, but the real impact of bloodsucking comes later. Along with the anticoagulants, to keep its
mouthparts clear the bloodsucker can inject much more sinister substances, most notably the spores (technically called sporozoites) of malaria, sleeping sickness, Leishmaniasis and Chagas diseases;
the microscopic bloodworm larvae that cause elephantiasis; bacteria like Lyme disease, plague and typhus; and viruses like yellow fever, dengue and encephalitis. For humans
the importance of bloodsuckers is not in the tiny drop of blood that they remove, but in the legacy of the diseases that they can leave behind.
Different bloodsuckers have evolved relationships with different diseases. Quite often it is only one particular species or closely related group that is implicated, and the species involved
vary from one part of the globe to another. Anopheles mosquitoes can spread malaria, whilst Aedes mosquitoes are vectors of yellow fever and dengue. Ticks are carriers of Lyme
disease. Fleas spread plague. Body lice carry typhus. Many of these formerly dreaded diseases are now understood, and some have been eradicated or at least are controlled in parts of the world.
Ague, the traditional English name for the endemic malaria of East Anglia, disappeared from the UK in around 1900, and was gone from southern Europe and the USA by the 1950s. Malaria is still
extant in many tropical countries, but has long been treated with quinine and other antimalarials. This is fine for wealthy Western tourists, but expensive enough to be out of the reach of many,
and malaria still kills roughly 700,000 people a year, mostly children in Sub-Saharan Africa. Plague is now the stuff of history books and nursery rhymes (unless you live in India, Africa or
Madagascar). Typhus is merely a dark memory from the itchy days of lice-infested clothing; nothing to do with head lice, thankfully (except, perhaps, in Ethiopia or Peru). It is too easy to be
smug, especially in the comfort of our civilised homes. In the West we may have conquered many of these diseases, but there is still opportunity for the same painfully biting bloodsuckers to visit
us, and the diseases they carry have not stopped evolving.
THROUGH THE CURTAIN – THEY CAN SMELL US IN OUR SLEEP
Anyone who has wandered marshes on a warm, sunny day will know how quickly mosquitoes appear, and hover in a cloud around the head. In the open they, together with horse-flies,
cleg-flies Haematopota pluvialis and other biting flies, are attracted to your silhouette presented against the open sky. This is, after all, one of the best ways of
finding a cow or horse, or other blood-filled animal, out in the fields. This strategy does not work inside a building, but mosquitoes have another prey-detection method – smell.
Humans, like all mammals and birds, breathe out carbon dioxide, a gas that mosquitoes can detect at very low concentrations with special chemoreceptor organs on their antennae. They can also
distinguish between a constant low-level background concentration, such as that given off in general decay from the soil and leaf litter, or from fires, and the characteristic regular pulses given
off during animal breathing. Again, like silhouette hunting, this is a long- to medium-distance detection technique working best out of doors, but carbon dioxide also acts as a trigger, enhancing a
mosquito antenna’s sensitivity to human skin odours.
Humans (and other animals) give off many different aromatic chemical signals, although they may be imperceptible to us today, after we are showered and bathed clean at regular intervals. Our
noses are no longer the most sensitive organs anyway. If we take a big sniff of purified skin chemicals collected in a laboratory vial, we might just about notice a hint of fruity musk, but insect
antennae work at the level of detecting just a few airborne molecules. Despite soap, eau de toilette, deodorant and expensive perfumes, it is by smelling us out that mosquitoes can find us indoors,
in the dark, when we sleep. Once inside the house, finding us to bite is relatively easy; it is finding a way in through the doors in the first place that was their greatest ecological jump.
Mosquitoes lay their eggs in fresh water – rivers, ditches, lakes, ponds, puddles – and their wriggling larvae feed on tiny morsels of decaying organic matter in the murk. When they
hatch into adult flies, the males are happy to visit flowers to drink nectar for energy, but the females must take a vertebrate blood meal to get enough protein for the eggs developing in their
ovaries. Finding a natural marshland animal like a buffalo or horse by its silhouette and carbon dioxide puffs is easy enough, so why venture into the dark confines of a human shelter? This, at
first, seems unlikely behaviour for a swamp-inhabiting fly.
Mosquitoes, however, are a widely diverse group (Jones 2012), with many thousands of different species around the world, and although most live and bite outdoors, there are
plenty with alternative behaviours. Away from the marshes a few species lay their eggs in the flooded rot-holes in old trees, where a branch has fallen and the heartwood has rotted away to form a
dark cavity that fills with rainwater. Others will utilise small puddles, water-filled hoofprints, ruts, drains or blocked gutters. Some species feed during the day, others roost in sunlight,
seeking out a rock crevice, small cave or dark shade from hanging leaves and dense branches under which to hide so that they can feed at night. Similar dark, dry spaces offer overwintering sites to
adult mosquitoes. In the end it is no surprise that among all their variety, some inquisitive mosquito species were ready to fly in through an open window into the interior darkness as soon as
houses were built.
Instinctive house-entering behaviour is under genetic control. In East Africa the yellow fever mosquito Aedes aegypti, a major vector of dengue virus, is very common and widespread,
living near human habitation and also well away from it in the wilderness. Laboratory breeding and release studies showed that domestic larvae collected around buildings, living in water dregs in
old pottery, tin cans and animal troughs, produced adults more likely to enter buildings to feed; feral larvae collected from tree-holes in the jungle were less likely to do so (Trpis and
Hausermann 1978). The clincher is that peridomestic larvae, living in between, in the steps cut into the trunks of coconut palms, were intermediate in their behaviour and may be genetic hybrids.
There is no simple on/off switch for house entering; like most complex behaviours, it is under the control of many genes, the understanding of which is still some way off. Nevertheless, there is
often a close link between a mosquito species being an indoor biter and breeding in small water pockets close to human habitation.
It is tempting to suggest that the arrival of pottery in human prehistory, around 10,000 years ago, could have been a major advance for mosquitoes, as they found discarded broken but flooded
receptacles in which to lay their eggs right on human doorsteps – in the septic fringe rubbish midden perhaps. This much is speculation, but in a strange twist, a
possible recurrence of these potential human/mosquito relations is going on in modern-day Queensland, Australia. A decade of droughts has encouraged householders to store rainwater in garden
containers, and this has increased the numbers of mosquitoes breeding there (Trewin et al. 2013). There are fears that this mirrors the container-breeding fauna when the yellow fever
mosquito was more prevalent in the area, particularly from 1904 to 1943, when dengue epidemics occurred.
During the malaria and yellow-fever reduction campaigns of the early 20th century, mesh screening of water tanks and the removal of rubbish from the streets was a key tactic to reduce the
availability of mosquito breeding sites in disease-oppressed towns and cities (Boyce 1910). Flooded tin cans littering the streets are still a minor problem in some places today, and water slops in
secondhand tyres could herald a major disease epidemic in the 21st century. The Asian tiger mosquito Aedes albopictus, named for its pretty banded patterning and aggressive biting
behaviour, has been spread from its original native range in South-east Asia, into southern Europe and much of the USA, and it is making inroads into South America and West Africa. Its aquatic
larvae have been accidentally transported about the globe in the rainwater accumulating in secondhand tyres (Hawley et al. 1987). There is a major world trade in reusing and remoulding the
tyres, but because they are hardy and non-perishable, they are liable to be left on docksides, uncovered, in all weathers. They soon accumulate pockets of rainwater and are easily accessible to
egg-laying mosquitoes.
The Asian tiger mosquito is a noted urban resident, breeding in many different flooded containers as well as tyres. It readily enters homes to bite people, and spreads dengue and chikungunya
fever, and West Nile virus – all debilitating and sometimes deadly maladies. At the time of writing this book Australia and New Zealand are on full Asian tiger mosquito
alert. The mosquito has been intercepted at several seaports, and has already become established in the Torres Strait Islands just off the Queensland coast (Ritchie et al. 2006).
Litter in the form of flooded pots, tin cans, broken jam jars, tyres and other rubbish is not always necessary to sustain populations of house-invading mosquitoes. Throughout the world some
species are generally more prone to come indoors than others, and almost inevitably many have acquired major importance when it comes to biting humans and spreading human diseases. Detailed study
of British mosquitoes during the 1930s showed that what was at first thought to be a single species, Anopheles maculipennis, was actually a group of closely related sister species. Two
species were virtually identical as adults, but could be distinguished by the patterns on their floating egg masses. One form, A. messeae, laid its eggs in inland pools, hardly ever bit
humans and was not a disease carrier. The other form, A. atroparvus, laid its eggs in coastal marshes, often came into houses to roost, frequently bit humans and was historically
responsible for spreading ague (malaria) in lowland England (Edwards et al. 1939).
The sinisterly named Culex molestus has taken indoor biting to an extreme. On the face of it almost identical to the globally common and widespread Culex pipiens, even under a
microscope, this ferocious biter first came to the attention of medical entomologists when the beleaguered citizenry of London took to sheltering in the deep railway platforms of the London
Underground to escape the nighttime bombing during the 1940–1941 Blitz (Shute 1951). DNA studies show that it is distinct from the surface-dwelling C. pipiens, and has adapted to
breeding in the rainwater puddles along the subterranean rail lines. Such is the isolation of different populations in the tunnels that different branches of the underground
railways are now evolving genetically different strains (Byrne and Nichols 1999).
C. pipiens normally feeds on bird blood, but C. molestus bites mammals – the mice and rats infesting the tunnels, and the daily herds of human commuters and shelterers.
It also breeds all year round in the mild, temperature-stable tunnels, rather than just in summer, a characteristic also noted in similar C. pipiens/C. molestus species complexes
in Croatian cellars, Portuguese caves and several other metropolitan subway systems in North America, Japan and Australia (Merdic and Vuljicic-Karlo 2005). There is more to this behavioural
plasticity than mere annoyance at yet another human-biting mosquito species. Intermediates between C. pipiens and C. molestus occur where the populations overlap. The exchange of
one type of host (birds) for another (humans) may just be enough to transfer blood-borne diseases, too. C. pipiens is a major vector of bird arboviruses; Japanese encephalitis and West
Nile virus are arboviruses from this same group, and they have recently become important human diseases.
THE BED BUG – IT BITES US IN OUR BEDS, OBVIOUSLY
Bed bugs do not spread human diseases, but they cause no end of headache. Cimex lectularius, to give the aptly named bed bug its modern scientific name, is a broad,
round, flat, reddish-brown wingless insect. It is also called wall-louse (for its habit of hiding under wallpaper), red-coat (for its blood-filled colour), crimson rambler (likewise) and mahogany
flat (it is, indeed, very flat).
This is the notorious bloodsucking bug that infests cheap hotel rooms the world over – and some not so cheap ones, as I discovered in the elegant but faded grandeur
of a hotel in the Sri Lankan capital Colombo some years ago. It hides during the day between the planks of a bedstead, or tucked into the folds of sheets, but sneaks out to bite at night. Its
presence is usually only detected the morning after a stay in a room where it is present, when the red welts left at the puncture wounds or some spilled blood on the bed sheets are discovered.
At only 5.5–7mm long, the bed bug is quite small, but it can drink a huge amount of blood in comparison to its body size. An adult female weighing 6mg unfed was able to consume nearly 14mg
of blood (Goddard 2009). She could do this because she has an enormously flexible body. Although flat to start with, the abdomen of the bed bug has wide, elastic membranes between the hard armour
plates. As the bug feeds the abdomen swells grossly into bloated satiation.
The main medical (and veterinary) importance of bed bugs is in the sheer volume of blood extracted, with victims living in highly infested conditions (5,000 bugs per bed have been reported)
receiving many hundreds or thousands of bites nightly. In one particularly gruesome account a homeless semi-destitute man was living in a single room alive with many thousands of the bugs, some of
which were lodging under his uncut curled toenails and between his toughened and filth-impregnated toes (Burgess and Cowan 1993). Blood loss can become very significant, leading to iron deficiency
and anaemia, not to mention irritability from disturbed sleep. The emotional distress can be misdiagnosed as neurosis, or it can lead to costly lawsuits from disgruntled wealthy guests of luxury
hotels. How things have changed.
When my father, aged 14, manhandled a secondhand bed through the bombed-out streets of Shepherd’s Bush and Paddington on a borrowed costermonger’s barrow in 1944, he was pleased with his thrifty purchase, but not at all surprised when blood spots appeared on the sheets a few days later. Unlike the surgical precision of a mosquito, bed bug
feeding is a brutal and imprecise action, and repeated probings with the rather stout, blunt stylet mouthparts often leave a trail of adjacent small bites before the true feed puncture is made.
Instead of panicking or trying to sue someone, my father and his mother set about stripping and dismantling the bed, cleaning it and removing the vermin. In a time of hardship and deprivation, this
would have been completely normal.
Bed bugs went through a bit of a slump in the second half of the 20th century, and a nuisance insect that everyone had heard of, even though they may not have necessarily been pestered by it,
appeared to be in terminal decline. A modern lack of public awareness and the insects’ resistance to chemical insecticides may explain why the bugs are making a comeback today, but it is
their evolution in the long term, how and when they first started biting human beings, which is even more fascinating. For whether they are hidden in the plump mattresses of five-star hotels, or in
the cramped palliasse in a wayside tropical camp, one question keeps arising: where did bed bugs live in the first place, before we humans offered them our blood, and before we had beds to sleep
on?
John Southall, writing his Treatise of Buggs (1730) thought he knew – they lived on trees, more particularly ‘Firr’ trees, and he assured his readers that the sap of
deal in particular was ‘one of their beloved foods’. Nonsense, of course, but Southall had his reasons for stating this. He was shamelessly advertising a concoction to destroy the bugs
– his ‘Nonpareil liquor’ – and by way of self-promotion he wrote his pamphlet about their life cycle, their increasing numbers, their destruction and, most intriguingly,
‘when and how they were first brought into England’. He pinpoints their arrival directly to the 1670s, blaming the traders whose ships daily sailed into British ports bringing
‘chests and casks, linnens and paper’ riddled with the insects. He makes the astute observation that port towns and cities are thick with bed bug infestations, but villages further
inland are less troubled, if at all.
There were certainly widespread reports of bed bugs in and around the metropolis in the decade following the Great Fire of London, in 1666, and one of the usual stories has
it that they arrived with building timber (notably deal) imported from the Americas. The bug’s arrival in the 1670s is now well established, but this was not the first time it had appeared in
England. Remains of bed bugs were dug from a pit dated to the 2nd century AD in the Roman town of Alcester in Warwickshire, and there is a tale (though highly likely to be apocryphal) that King
John (1199–1216) was troubled by them at Kingsclere in Hampshire.
The first real evidence of bed bugs’ occurrence comes from the writings of Thomas Moufet (sometimes Moffet or Muffet, stepfather of the Little Miss of nursery rhyme curds-and-whey fame),
who clearly and accurately describes the ‘wall louse’ in his Theatre of Insects published posthumously in 1634. It recounts how the bugs were troublesome to two ladies of a
noble family at Mortlake, Surrey, in 1583. The high status of the victims’ family is no mere name-dropping snobbery on the part of Moufet. Their social standing says much about the fact that
bed bugs need the warmth of a well-heated house to breed and multiply to pest proportions; and at this time they were unlikely to be found much in the unheated hovels of the English peasantry.
There seems little doubt, now, that bed bugs had probably crept into Britain since time immemorial, but that they did not become established enough to warrant major pest status until the late
17th century, when John Southall patented his liquor.
An American or at least a Caribbean origin of the bugs is hinted at by Southall, who claims to distinguish between American and European bugs – the former slightly larger, the latter a
smaller degenerate form. The New World source of the bed bug suited Southall’s New World Nonpareil Liquor. He was able to charge two shillings a bottle for it, enough to treat a ‘common
bed’. That was more than the weekly wage of the servant who might be applying the treatment.
However, contrary to Southall’s supposition, bed bugs were firmly rooted in the Old World. They were recorded from Italy and Germany in the 11th century, and France in the 13th century.
They were well known in classical times, when they were called koris (a name still used for many plant bugs today) and cimex, the official scientific name
entomologists now apply to bed bugs. The bed links to the bloodsucker were already known to the Ancient Greeks five centuries before Christ, and are discussed by Aristotle, Aristophanes and others
(Beavis 1988). Bed bug remains have recently been found in archaeological excavations in Egypt. Beyond Ancient Egypt written records are lost and subfossil remains are scant, but an extrapolated
history of the bed bug can still be guessed at by examining the modern insects and their relations to other, similar species.
Although C. lectularius is the human bed bug of choice in temperate latitudes, it is replaced by the very similar, but subtly different, C. hemipterus in the tropics. There are
also another 16 species (at least) of Cimex known across the world, and a further 70 or so bloodsucking bugs in the bed bug family Cimicidae. They all have similar broad, round body
shapes, all are wingless and all feed by sucking vertebrate blood. More particularly they attack bats and birds. Even more particularly, they attack bats, pigeons, swifts, martins and swallows
– birds that, as already noted, originally nested in caves and on rock-faces, long before humans had emerged and built the first houses or laid down on the first beds. Caves, it seems, are
where humans (and birds) first picked up these bugs, and it is likely that bats are the original hosts. Incidentally, bats are also blamed for being the original hosts for the fungal diseases of
ringworm and athlete’s foot. But it is their gift of bed bugs, however, that we should most resent.
It’s temping to speculate that for millions of years progenitor bloodsucker bugs feasted on the blood of the bats that roosted in a roughly weathered rock cavern somewhere in the East
African savannah, when one day a tired primate shuffled in and slumped down onto the floor. To the bugs it was just another food source to be exploited. They have continued to exploit it to this
day – it’s just that now, rather than scuttling off into rock crevices, the bugs find perfect shelter in the joints of bedsteads, the cracks in floorboards, and the tight spaces behind
peeling wallpaper and loose skirting.
BUGS AND BUGBEARS – NIGHT-TIME NUISANCES, PAINS IN THE BUTT
In a nice etymological, rather than merely entomological, twist C. lectularius was the first insect, courtesy of Mr Southall’s informative pamphlet, to achieve
the common English name ‘bug’. Nowadays almost any insect, or indeed any invertebrate from giant squid to bacterium or virus, can loosely be called a bug, but to entomologists true bugs
are really only those insects, with sucking rather than chewing mouthparts, that are in the order Hemiptera. This is the group that includes shieldbugs, stinkbugs, water boatmen, pond skaters,
aphids, leaf-hoppers and scale insects. Most of these are plant feeders, using their tubular mouthparts to suck plant sap, but a large number have evolved predatory behaviour, skewering other small
insects and sucking out their innards. Not surprisingly, the Hemiptera have also produced bloodsucking insects like bed bugs. This probably arose from insect-feeding bugs living in animal nests
where they fed on fly maggots, flea larvae, beetle grubs and each other, but occasionally taking an exploratory poke at a nest owner’s flesh, almost by accident, in the darkness. A small
relative of the bed bug, the debris bug Lyctocoris campestris, lives in barns, haystacks and the odd grain store, feeding on the other insects in there, but can give a sharp nip if picked
up (Busvine 1976).
Before Southall, the term ‘bug’ really meant a bugbear, similar to bogeyman (sometimes bogie or boggart), and usually referred to some ill-formed neurotic worry or night terror,
although it was sometimes personified into the shape of a hobgoblin. Whether Southall picked up his usage from reports of night-time feeding of the bed bug is not completely clear, but it is during
the night that humans are most susceptible to vampire feeding. Vampire bats, three species in the Central and South American family Desmodontidae, occasionally roost in decrepid old buildings, but
they mainly feed on wild and farm animals. Human victims are usually limited to the unfortunate homeless poor, or campers sleeping out in the open. However, there is a group of true bugs for which
the term ‘vampire’ is much more appropriate.
The assassin bugs are a large and diverse group of Hemiptera, well named for their aggressive predatory behaviour. They are often large and stoutly built insects, with long
legs to move stealthily and grip firmly, and powerful stabbing mouthparts. Most feed on other insects, caterpillars, maggots or worms, but several have adapted to sucking the blood of birds and
mammals, including humans. The widespread European species Reduvius personatus, often called the masked hunter or fly bug, occurs in old houses and also some commercial premises, and
although it mainly feeds on other household insects (bed bugs are a favourite), it can give a painful bite if carelessly picked up, and will also take advantage of the sleeping human form to drink
down a little of the body’s red liquor.
Elsewhere in the world larger and even more aggressive assassin bugs can become a real problem. In Central and South America several species of Panstrongylus, Triatoma and
Rhodnius are called kissing bugs because of their habit of biting the faces of human sleepers, especially near the eyes. They hide during the day in crevices around a bed, or in the folds
of bedclothes. Their bite, or resultant swelling afterwards, is very painful. This is not just down to the irritant prick or injected blood anticoagulants. The bug’s faeces get rubbed into
the wound, or into the eyes (notably in children) causing the eyelids to swell – Romaña’s sign, named after the Argentinian doctor who first noticed the phenomenon.
Kissing bugs also spread the parasitic protozoan Trypanosoma cruzi, known as Chagas disease after the Brazilian physician who first described it in 1909. Once injected into the body the
parasite multiplies in the lymphatic nodes and muscle tissue, causing glandular swellings, fever, fatigue and body aches. Then large numbers of infective stages are released
into the bloodstream, for another assassin bug to pick up for onwards transmission to yet more victims. Although people can live apparently symptom free for many years, chronic infection can lead
to serious disorders of the heart and digestive tract, and may eventually be fatal.
Kissing assassins cannot always get a human blood meal. They have been found in the burrows of various native rodents, such as house mice and black rats; others live with communal hole-nesting
birds like pigeons. The broad, flat young (nymphs) are covered all over with a sticky substance, and they disguise themselves by coating their bodies with sand, dust, fluff and other debris –
a good technique to enable you to hide if you are living right inside the den of your victim.
Sleeping, far from being the restful recovery we might expect, can be a dangerous business. At least rough beds raised above the dirt give some protection from attack (although bed bugs and
assassin bugs are good climbers). In areas of tropical Africa, maggots of the deceptively cute-sounding tumbu fly Cordylobia anthropophaga and the Congo floor maggot Auchmeromyia
luteola come wriggling out of the bare, dusty ground looking for a tasty mammalian meal. The adult insects, about the size of blow flies, lay their eggs in the soil, especially if there is
contamination with faeces, but also in damp clothing or bedding.
The tumbu fly grub will, if it has a chance, burrow into the flesh of the cheeks, arms, lower back or buttocks, causing a boil-like swelling in which it feeds for two weeks before popping out
and pupating. The congo floor maggot prefers to pierce the skin and drink the dribbling blood. It is well adapted to its intermittent feeding opportunities and has the
accolade of being the fly larva able to withstand the longest fast between meals, surviving 48 days in laboratory tests (Garret-Jones 1951). The original hosts for both species were probably wild
animals, particularly burrowing warthogs, aardvarks, hyenas and wild pigs, but they now commonly attack dogs and chickens, so the flies are often near domestic dwellings. It is us humans, literally
being eaten alive, who are generally regarded as being the primary hosts today. The rest of the world should be perennially thankful that neither the tumbu fly nor the congo floor fly followed
humans on their long migrations out of Africa.
