Accrediting Dry Zone Chronic Kidney Disease of Unknown Etiology to
Zoonotic – Borreliosis – “Lyme Disease”
Tallying the Chronic Kidney Disease (CKD) epidemiology with Zoonotic Interaction areas of Dry Zone Sri Lanka
Wherever there is a very close interaction between wild and semi-urban areas in plenty, there is the avid opportunity for the emergence of Zoonotic diseases among the adjacent human population; it can be an entirely a newer disease or be a known disease that is afresh to the local area or greater geographical territory. The Dry - Zone of Sri Lanka has got very vast wild reserves that are always being cleared most of the time illegally than legally for various livelihood practices of the human being – and this emancipates the semi urban-wild vivid interaction. Human in pursuit of cheaper and easy livelihood and extras, shepherd their larger herds of neat-cattle, goats, and buffaloes through the wild reserves, - these (semi)domesticated ungulates and the dogs the trustworthy companion of man for centuries come back to urban and semi-urban areas for night paddocking establishes the strong and constant interaction with human population, at times directly as well by way of hunting rabbits, squirrels, wild ungulates, firewood collection etc. All these horizons for newer zoonotic diseases abundantly occur in the entire Dry-zone districts of Sri Lanka especially of Anuradhapura, Polonnaruwa, and Puttalam districts e.g. areas Kalawewa, Naachchiadhuwa, Nuwerawewa, Kiribhava, Kekirawa, Gritalae, Kiranthrukotte Galkiriyagama, Navawaththegama, Karawilagaswewa, Erabhudhugaswewa etc. and list prolongs covering the other dry zone districts.
Elephant distribution represents the wildlife reserves Mahaweli development represents Zoonotic interaction areas
Further wildlife interaction
Lyme disease – Borreliosis caused by spirochete bacteria Borrelia first reported as recently as1977-1980, when it was found in the mid-gut of Ticks. It is a member of the same group of spirochetes that causes leptospirosis,(Leptospira interrogans) relapsing fever (several Borrelia spp) and venereal disease (Treponema pallidum) which were well-known to medicine long before. Since the first reporting, the bacterial agent of Lyme disease and the disease itself has been undergoing serious research study because of its notoriousness to be worldwide distribution. This cosmopolitan distribution is attributed to the most important predominant vector, a hard-shelled slow blood-sucking tick Ixodes species that is capable of surviving variety of climatic conditions and hanging on to a variety of newer hosts – animals, man, birds particularly those of always migratory marine nesting colony of birds, even plants and inert materials coming into contact and its’ ability is well described below.
BORRELIA ORGANISM – THAT CAUSES LYME DISEASE – BORRELIOSIS
Dr. Willy Burgdorfer and coworkers observed spirochetes in the mid-gut tissues from ticks collected in a Lyme disease endemic area. These spirochetes produced a skin rash resembling erythema migrans of the human when injected into rabbits, and sera from Lyme disease patients reacted with the bacteria in indirect immunofluorescence assays. In recognition of this discovery, the bacterium was named Borrelia burgdorferi - though it was described as a bacterium, it is a complex of nineteen genotypes – and only three of them responsible for the disease in different geographical regions. The whole lot of the complex is called – the Borrelia burgdorferi sensu lato complex; and the three of those are identified as most important pathogens: B burgdorferi sensu stricto (North America, Europe), B afzelii (Europe, Asia), B bavariensis, or B garinii (Europe, Asia), all of which are “pathogenic” for human. Only B burgdorferi sensu stricto has been proven so far to be “pathogenic” for domestic animals such as cattle, buffaloes, horses, sheep, dogs, and cats.
Another member of the genus Borrelia; B miyamotoi is the bacterium causing relapsing fever, characterized by clinical signs such as fever, headache, fatigue, and muscle aches, although transmitted by Ixodes ticks and louse, a completely different zoonotic disease to that of Lyme disease Borreliosis in animals and human.
MORPHOLOGY of SPIROCHETE BORRELIA AND PATHOGENESIS OF LYME DISEASE
The flagella of spirochetes traverse the length of the cell body and are “hidden” beneath the outer membrane, in contrast to other organisms that have external flagella radiating outward. A potential advantage of this highly conserved flagella arrangement of all spirochetes is shielding the vividly immunogenic flagella from the host immune system.
The Lyme disease spirochete Borrelia burgdorferi has 7-11 flagella attached near each end of the "protoplasmic" or cell cylinder, with each flagellum extending through the periplasm towards the center of the spirochete. The flagella impose a flat-wave shape (not a spiral shape!) on B. burgdorferi by wrapping around its protoplasmic cylinder.
The morphology and motility of spirochetes allow these organisms to swim in highly viscous media that immobilize other bacterial species. B. burgdorferi progresses onto a disseminating stage after a prolonged latent period of 5 to 6 weeks after a tick bite, when the pathogen travels away from the site of the tick bite through the bloodstream and/or lymphatic system to invade and colonize various tissues, such as the heart, synovial fluid of joints, urinary bladder and the nervous system. Motility along with Chemotaxis of the B. burgdorferi towards disintegrating Extra-Cellular Matrix constituents such as integrin, Fibronectin, glycosaminoglycan, and collagen play a major role in the process.
In contrast to those of free-living bacteria, or other pathogens, the genome of B. burgdorferi is relatively small, probably reflecting its lifestyle as an obligate parasite hence B. burgdorferi lacks the conventionally recognizable machinery for synthesizing nucleotides, amino acids, fatty acids, and enzyme cofactors, completely scavenging these metabolites and biochemical intermediates, such as simple sugars, fatty acids, purines and pyrimidine, peptides and various metallic ions, and are chemically utilized and/or modified to provide an intracellular pool of compounds necessary for protein, nucleic acid, membrane and cell wall biosynthesis from the host.
The limited metabolic capacity of B. burgdorferi requires a complexity of genome groups for its survival as a complete parasite and chemically demands undefined growth medium and longer period as long as 6 weeks for in vitro cultivation.
Also B. burgdorferi sensu stricto bacterium completely lacks the secretion virulence factors common to many bacterial pathogens, such as lipopolysaccharide, toxins, proteinases and specialized secretion systems, but are capable of producing variety of surface proteins through markedly different gene expressions that allows itself to replicate and survive within different hosts and establish within a variety of tissues of the same host for longer periods.
B. burgdorferi outer surface proteins are differentially regulated in response to host conditions. Spirochetes remodel their outer surface in different host environments, represented above by different colors. In the unfed tick, B. burgdorferi (represented in blue) produce a variety of proteins, such as OspA, to persist within the tick mid-gut for extended periods of time. Once a tick has attached to a vertebrate host, B. burgdorferi (now represented in red) expresses other proteins (e.g. OspC) in preparation for transmission to the new host. During infection of the mammalian host, B. burgdorferi (colored in yellow) expresses a variety of other proteins (including VlsE), presumably to survive the attack by the host immune system, disseminate to distant sites within the host, and acquire specific nutrients. Above figure shows representative proteins only and is not meant to be a comprehensive list.
Thus B. burgdorferi is not an ideal pathogen but an obligatory scavenging parasite for nutrient requirements; in contrast, the bacterium produces multiple molecules that activate host responses and can lead to localized and generalized inflammatory pathogenic responses. Most of these host responses normally function to contain or clear the infections and are components of the innate and/or cellular inflammatory response; although the whole purpose is to clear the infection, if continually activated, they lead to lesion development and disease and thus Lyme disease is an outcome of innate and cellular mediated immune responses to the spirochete infected tissues – most probably by induction of cytokine/chemokine expression by ever changing bacterial Osp lipoproteins and the resulting recruitment and activation of lymphocytes, macrophages and granulocytes play a major role in both local histopathology and constitutional symptoms. Despite their relatively low densities in tissues, Borrelia cause neurologic, cardiovascular, arthritic and dermatologic manifestations during the disseminated and persistent stages of infection
B. burgdorferi’’s several Outer-surface-proteins(Osp) that selectively adhere to host platelets, chondrocytes, endothelial cells cell surface proteins and extracellular matrix components are involved in the homing of Borrelia to histologic compartments within each tissue; adherence to endothelial cells and Osp penetration of blood/ lymphatic vessels facilitate migration to tissue strata at distant sites through activation of plasmin on the bacterial surface and induction of host proteases that in turn elicit/facilitate inflammation process as well. Adherence with disintegrating extracellular matrix via specific interactions to effectively evade the antibodies of the host and contribute dissemination into the various tissues which are also, in turn, ensures eliciting the contineuous immune response - drains away the normal function of the tissues and damaging lesions are set in motion. Therefore the severity of the Lyme disease is a balance of power in the struggle between host’s total defense mechanism and the capability of B. burgdorferi to survive the immune response as well as its ability to perpetuate eliciting innate and/or cell-mediated immune response from the host. The striking feature of this pathogenicity is that tissues differ in prioritizing the type of immune response whether it is cell-mediated or innate response within a single host – e.g. endothelium may warrant predominantly innate and the pericardium will be dominated by the cell-mediated response.
CLINICAL SIGNS OF DOMESTIC ANIMALS
Owing to the logical difference of - Pathognomonic immune response clinical signs are unspecific and numerous clinical signs have been manifested in domestic animals; includes limb and joint diseases, neurologic, cardiac, and renal abnormalities all reflective of numerous adhesions produced by Borrelia burgdorferi present in the respective tissues thus clinical signs are appropriate for the organ system. Routine laboratory tests, such as Complete Blood Count (CBC), Blood Chemistry, and Radiograph etc. confirming nothing shall arouse the suspicion of a Borrelia infection.
Most common clinical syndromes in dogs - lameness, shift limb lameness, fever, anorexia, lethargy, and lymphadenopathy, with or without swollen painful joints. Renal Borreliosis is the second most canine syndrome, characterized by uremia, hyperphosphatemia, and severe protein-losing nephropathy, accompanied by peripheral edema and is generally fatal. Rare cardiac forms manifest typical Conduction Abnormality and bradycardia. Facial paralysis and seizure disorders in the neurologic form.
In horses swollen joints, polyarthritis, lameness, laminitis, persistent mild fever, muscle stiffness, anterior uveitis, and in pregnant mare abortion, delivering weak foals that die soon, sudden embryonic loss and failure of conception. Nervous forms manifest depression, behavioral changes, dysphagia and chronic weight loss in all form the disease.
Cattle – chronic weight loss, polyarthritis, lameness and persistent mild fever; in acute Lyme disease fever, stiffness, swollen joints, drop in milk production, erythema of udder and skin between digits. In sheep lameness, swollen joints, un-thriftiness, and persistent fever.
DIAGNOSIS AND CONSTRAINTS
Diagnosis should be approached through epidemiological considerations, history of tick exposure, livelihood, clinical signs, - elimination of other diagnoses based on clinical signs such as autoimmune disease and progression to antibiotic therapy. Clinical signs are appropriate for the organ system while autoimmune panels, CBC, blood chemistry, radiographs, and other laboratory tests return normal picture, with exception to direct tests for affected organs – e.g. uremia in renal disease, - ECG for heart block in cardiac disease. All immunological assays only indicative exposure to the organism, but serologic testing for B burgdorferi antibodies shall guide the clinicians for clinical diagnosis. Long incubation periods, the persistence of antibodies for months and years, and disassociation of antibodies during clinical disease make the diagnosis by blood testing alone impossible. Persistence of antibodies after therapy, the similarity of electrophoresis (western blot) profiles in all stages of disease and convalescence demonstrates the limitation of the serology in diagnosis. Detection of B burgdorferi from aseptically collected fluids of joints, articular tissues, cerebrospinal fluid and urine under dark-field microscopy or IFA aid diagnosis. Currently Polymerase Chain Reaction test to detect the DNA of flagellin gene of Borrelia burgdorferi in urine samples is being used to initiate therapy as well as to monitor the therapy progress with grand success.
Culture requires 6 weeks incubation and highly specialized media, thus useless for clinical purpose, can only be employed for long-term strategy investigations.
Treatment
Antibiotic therapy is indicated in all cases with clinical signs attributed to Lyme Borreliosis. Antimicrobials in the tetracycline (e.g. doxycycline 10 mg/kg, PO, bid) and penicillin e.g. amoxicillin 20 mg/kg, PO, TID) groups are effective, and rapid response is seen in limb and joint disease in most cases, although incomplete or transient resolution of signs occurs in a significant number of affected animals. Doxycycline is preferred over penicillins because of mixed infections with other tick-borne pathogens such as Rickettsia, anaplasma and Bartonella are often found in animals with clinical signs. Clinical and research data indicate that low-level infection in animals, including people, may persist despite antibiotic therapy. In dogs, standard antibiotic doses for 4 weeks have been demonstrated to be effective. If clinical signs recur, the antibiotics mentioned above can be used again, because of the persistent infection is not the result of acquired antibiotic resistance but of delayed exacerbations. Prolonged antibiotic higher range therapy more than 4 weeks may be beneficial for animals with continuing disease signs, which can be monitored by nested Polymerase Chain Reaction for certain gene sequence DNA of causative organism present in the urine.
Symptomatic therapy directed toward the affected organ system and clinicopathologic abnormalities is also important, especially in renal disease. In limb and joint disease, the use of NSAIDs concurrent with antibiotic therapy may lead to confusion over the source of clinical improvement and make a diagnosis based on therapeutic response difficult.
For horses Procaine Penicillin (30 000 to 45,000) IU/kg IM daily for 10 days, followed by Benzathine Penicillin every other day for 2 weeks or Oxytetracycline (6 -12) mg/kg i.v. for 3 weeks has been very successful. Above line of treatment for cattle, but up to 3 weeks very satisfactory.
Transmission and Control
The predominant vector Ixodes species – of Ticks
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| The lifecycle of the Predominant vector Ixodes Tick |
All Ixodes strictly a three-host tick, inhabits temperate or tropical forest zones wooded or shrubby grasslands, marine nesting colony, that are always migratory and fewer are adapted to humid areas in semi-deserts or to Arctic or sub-Antarctic. The striking feature of these ticks is occupying cracks and crevices of inert materials, furniture buildings and living flora while resting (off feeding). The primary hosts are smaller mammals that live in burrows, caves, and dens – but regularly leave and come back to their place so that the tick rest until the next feeding. Thus Ixodes spp. is capable of adapting to a variety of animals as parasites and act as a vector for numerous infectious diseases to all ungulates as well as for the human. Lifecycle normally extends to 1-2 years but may prolong for 4 years depending on climatic genera and environmental temperature.
Ticks most frequently acquire spirochetes from infected rodents during their larval feeding. After molting to the nymph stage, infected ticks feed on a broad range of animals, including rodents, which become a new reservoir perpetuating the cycle. After the nymphs molt to the adult stage, they exclusively feed on larger mammals, which are often not competent hosts for B. burgdorferi. The spirochetes are rarely, transmitted trans-ovarian, so the larva and nymph feedings are crucial to maintaining the spirochete. Larva hatches from uninfected eggs laid on the soil, mainly feed on small reptiles, birds, and mammals. Nymph advances to feed on small and medium-sized vertebrates including birds and lizards – and the adults chiefly feed on herbivores and livestock, buffaloes and dogs; but all stages especially nymphs and adults parasitize humans to suck blood; the smaller size of the nymphs makes them difficult to detect and, hence, more likely to feed long enough to transmit the spirochete and cause Lyme disease.
Infection rates of the vectors vary according to region and season and can be as high as 50% in adult ticks. After a tick attachment, over 24 hours elapse before the first B burgdorferi sensu lato organisms are transmitted into the host’s skin. Steady infection of the host occurs after 53 hours into the first blood meal. Therefore, early removal of attached ticks reduces the potential for spirochete transmission. Therefore avoidance of ticks and exposure to it from wild areas is the best way to control. Owners of the dogs not complying with tick control is a worldwide problem despite the availability of plenty of easy application anti-tick preparations, such as collars, spot-on etc. Vaccination is impossible due to numerous antigen protein presented by the B burgdorferi though genome types serologically similar, all vaccines produced thus far has not produced desired results.
B burgdorferi sensu lato organisms are very adaptable to be transmitted by body fluids (urine, saliva, semen) or bite wounds. The urine of infected cattle from endemic areas carries the organism into a fresh farm, and have been reported infected without ticks or other insects. The trans-placental transmission has occurred from dams to puppies and foals, later culminates in mortality as well.
Other ticks such as Dermacentor variabilis, Amblyomma americannum, tabanid blood-sucking flies of horses and human, Mosquitos, and body lice can act as vectors for B burgdorferi sensu lato organisms, because of the organisms’ high adaptability for parasitism in the blood cavity of all insects. B burgdorferi is higher heat resistant than of lower heats, and effectively transmitted through venison and other meats of wild life origin; Hunting and skinning of larger herbivores, rabbits hares, and rodents directly expose the human and dogs to all stages of the Tick bites.
The importance of Borreliosis as a Zoonotic disease is increasing since only 10% of the dogs infected with B burgdorferi sensu lato organisms show clinical illness and the rest found to be either subclinical or just as reservoirs of infection for other domestic animals and human, and thus dogs pose significant threat as source infection for human than to its own. Similarly larger herbivores such as Buffaloes used for plowing muddy paddy-fields, along with marine birds wandering into muddy, marshlands, and freshwater lakes can act as subclinical – reservoirs of B burgdorferi.
Tick vectors of B burgdorferi sensu lato in the USA, Ixodes scapularis in the northeast and Midwest and Ixodes pacificus on the Pacific coast. I ricinus and I persulcatus are the primary vectors in Europe and Asia. The common animals that host the spirochete, as well as all three lifecycle stages of the ticks, are small mammals, most importantly rodents- mouse and rabbits, particularly white-footed mouse responsible for the maintenance of horizontal transmission of spirochetes since these animals are capable of contracting the spirochetes just through contacts.
by
Dr. S.Mhadeva,
Moblie Veterinarianary Surgeon UN-FAO
National Consultant Wildlife Veterinarian, Dept.of Wildlife Conservation,
Visiting Lecturer, Medical Microbiology, and Zoonotic Diseases
Faculty of Medicine, University of Jaffna. (Formerly)
