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1 Giardiasis Simone M. Cacciò European Union Reference Laboratory for Parasites, Department of Infectious, Parasitic and Immunomediated Diseases, Istituto Superiore di Sanità ESCMID Postgraduate Technical Wokshop Indigenous Parasitic Diseases in Europe Pavia, 6-8 May, 215

2 What is today s menu? Short introduction to the organism Taxonomy Diagnostics Epidemiology (molecular epidemiology) Clinical relevance of giardiasis Open issues and perspctives

3 Trophozoite Giardia Giardia is a flagellated, unicellular eukaryote, with a simple life cycle which comprises two stages: the trophozoite and the cyst Cyst THE ORGANISM

4 Binucleate (nuclei transcriptionally active) Large ventral disc used to adhere to intestinal cells Has metabolic pathways similar to those of prokaryotes Giardia: an unusual eukaryote Golgi apparatus not well developed Has mitosomes (derived from mitochondria) THE ORGANISM

5 Life cycle of Giardia Source: CDC THE ORGANISM

6 Taxonomy of Giardia More than 5 species of Giardia have been described on the basis of morphology. At that time, the assumption was: one host, one parasite In the 5s, Filice proposed a taxonomical scheme with only 3 species, mainly on the basis of the morphology of the trophozoite (median bodies). G. agilis G. muris G. duodenalis TAXONOMY

7 Species Taxonomy of Giardia Host G. agilis Amphibians G. ardeae Birds G. psittaci Birds G. muris Rodents G. microti Rodents G. duodenalis Mammals (including man) TAXONOMY

8 G. duodenalis is not a single species If we look at the morphology of cysts from different hosts, there is no variability, but a large amount of genetic variation is observed when isolates are compared at the level of protein (isoenzymes) or DNA. Many important studies on isoenzymes allowed to describe strongly supported clusters of isolates and defined genetic groups (or assemblages), most of which were comprised of isolates from specific hosts TAXONOMY

9 Genetic relationships based on isoenzyme data Genetic groups or assemblages Ass. G in rats Ass. C and D in dogs Ass. B in various mammals Ass. E in livestock Ass. F in cats Ass. A in various mammals TAXONOMY

10 Genetic groups Assemblage A Assemblage B Assemblages C, D Assemblage E Assemblage F Assemblage G Assemblage H Giardia duodenalis Host Man, primates, livestock, pets, wildlife Man, primates, livestock, dog, beaver, horse, rat, muskrat dog, canids livestock cat rat, hamster marine mammals TAXONOMY

11 Diagnostics tools Microscopy and staining procedures Immunologic-based assays Molecula-based assays DIAGNOSIS

12 Diagnosis: staining techniques Staining techniques have a relatively good sensitivity and specificity in the detection of Giardia cysts. They are commnoly used because of the low cost However, these techniques cannot be used to identify species (or assembalges) of the parasite, because of the lack of morphologic variation Giardia cysts Lugol DIAGNOSIS

13 Detection by immunofluorescence microscopy This method offers higher sensitivity and specificity compared to staining techniques. However, autofluorescent algae and other debris can cause cysts to be obscured when the sample is fixed to a slide, making difficult to confirm the diagnosis by phase contrast or differential interference contrast The antibodies do not differentiate between cysts from different Giardia species (or G. duodenalis assemblages) Cryptosporidium oocyst Giardia cyst DIAGNOSIS

14 Cysts Detection by molecular techniques DNA/RNA isolation Amplification by PCR RFLP Sequencing Real-time PCR DIAGNOSIS

15 Genetic markers for Giardia 18S rdna (genus-specific) ITS1 and ITS2, and 5.8S rdna (genus-specific) Beta-giardin Triose phosphate isomerase Glutamate dehydrogenase Actin Tubulin Histone Ferredoxin.and other genes DIAGNOSIS

16 Biological features influencing the epidemiology Small, environmentally resistant cyst stage Large animal and human reservoirs Ubiquitous, monoxenous, and able to cross-infect multiple species Low infective dose (1-1 organisms) Cysts are immediately infectious upon excretion Ability to multiply to very large numbers in a single host EPIDEMIOLOGY

17 General considerations on the epidemiology of human giardiasis Person-to-person transmission Zoonotic transmission (?) Waterborne transmission Foodborne transmission EPIDEMIOLOGY

18 Global burden of disease It is estimated that 5, new cases of giardiasis will occur every year The prevalence is higher in developing countries (2%) than in industrialised countroes (3-7%) Since 24, giardiasis has been included in the Neglected Disease Initiative to underline its link to poverty and the disease burden, paricularly in children A frequent cause of diarrhea in travelers

19 Giardiasis is a pediatric infection USA Source ECDC, 213 Age-specific notification rates of giardiasis cases in USA

20 Seasonality of Giardiasis No strong seasonal variation, a small peak in autumn

21 Risk factors: sporadic giardiasis UK study (Stuart et al., 23) Swallowing water while swimming Recreational fresh water contact Drinking treated tap water Eating lettuce Germany study (Espelage et al., 21) Gender (males more likely to be infected than women) Immunocompromised more likely to be infected Daily consumers of green salad Italian study (Faustini et al., 26) Exposure to surface water Travelling abroad High educational level WATER FOOD FOOD WATER TRAVEL

22 An overview of typing data in humans Location No. of samples Assemblage A Assemblage B Mixed A+B Europe North America Oceania Central and South America 35.4% 61.4% 3.2% Africa Asia % 55.4% 6.9% Higher prevalence of assemblage B, worldwide Higher prevalence of mixed infections in developing countries

23 Is giardiasis a zoonosis?

24 Assemblage E prevalent Assemblage A mainly AI Assemblage B almost absent Giardia in domestic animals Assemblage F prevalent Assemblage C rare Assemblage A (mainly AI) Assemblage B rare Assemblage C / D prevalent Assemblage B and B with varying prevalence in different surveys Mixed infections very common Assemblage-specific strains are more common in their respective hosts than zoonotic strains

25 Giardia in domestic animals Frequency of transmssion UNKNOWN Dog/Cat cycle Human cycle Direct or waterborne Direct or waterborne Frequency of transmssion UNKNOWN Livestock cycle

26 Wild carnivores Coyotes, wolves, foxes, ferrets Assemblages C / D commonly found. Assemblage A (mainly AI) also present. Rodents Beavers, muskrats, voles, wild mice Giardia in wildlife Hoofed animals Fallow deer, roe deer, reindeer, moose wild boars, water buffaloes Assemblage A, zoonotic subtype A I present but subtype AIII is more common and very distinct from those found in humans. Non-human primates Giardia microti is commonly found, beavers and muskrats also infected with assemblage B Non-human primates are infected with assemblages A and B, but most isolates are from captive animals

27 Giardia in wildlife The data indicate a minor role of wild animals in the transmission of Giardia to humans. Frequency of transmssion Likely to be LOW Human cycle Wildlife cycle(s) Direct or waterborne

28 AI AII AIII 1% Calf, sheep,cat, deer, human (4) Multilocus data for assemblage A Human, cat (1) 111 isolates Various species of deer (wild boar, cat) Phylogenetic relationships of assemblage A isolates based on 3 concatenated genes. The 3 main groups are strongly supported (boostrap values >98) Zoonotic transmission is not supported by these data

29 % Multilocus data for assemblage B 118 isolates Human, wildlife, monkeys No evident clusters related to hosts or sample origin are observed for assemblage B

30 Remarks on zoonosis Even studies performed in settings where interactions between animals and humans are common, have failed to provide evidence for a role of animals in the transmission of Giardia to humans

31 Is this true?

32 Transmission though water Giardia Standardised methods available USEPA method 1623 The Water Supply (Water Quality) Regulations 2 (SI 2/3184 ) EPIDEMIOLOGY

33 Giardia in the water Surveys of the occurrence of cysts have been performed in many countries. Cysts have been detected in surface water, ground water, springs and drinking water samples. Cysts have also been detected in wastewater from both developed and developing countries. In short, cysts are ubiquitous in the aquatic environment EPIDEMIOLOGY

34 Tongariro National Park, New Zealand Yes, Giardia is everywhere! EPIDEMIOLOGY

35 Sewage G. duodenalis ass. A G. duodenalis ass. B (Italy, USA, Norway) Surface water G. duodenalis ass. A (lake, Italy) G. duodenalis ass. B (river, Finland) Giardia in water samples Slaughterhouse wastewater G. duodenalis ass. A G. duodenalis ass. E (92%) (France) Reclaimed wastewater G. duodenalis ass. A (USA) No species other than G. duodenalis have been detected EPIDEMIOLOGY

36 Outbreaks, of course During the autumn and winter of 24 and 25, an extensive outbreak of waterborne giardiasis occurred in Bergen, Norway. Over 1,5 patients were diagnosed with giardiasis. Sewage leakage from a residential area is now considered to be the probable source of contamination The severe sewage contamination of a drinking water distribution network affected inhabitants in the town of Nokia, Finland in November 27 February 28. One of the pathogens found in patient and environmental samples was Giardia, which for the first time was detected as the causal agent of an outbreak in Finland. These outbreaks let us appreciate that Giardia circulates and persist in the enviroment, even in countries where its presence was condiered negligible

37 Outbreaks, and some unsual findings Illness was associated with having unintentionally swallowed contaminated water, and the risk increased with the number of mouthfuls of water swallowed. Confirmed aetiologies of infection included Giardia lamblia On 6 December 21 a fire in Hemiksem, Belgium, was extinguished by the fire brigade with both river water and tap water. A retrospective cohort study among 1 randomly selected households showed that 222 of 1187 persons had symptoms of gastroenteritis in the following week. Contamination of tap water with river water was the likely source of infection with Giardia, norovirus, rotavirus and Campylobacter These outbreaks let us appreciate that climatic changes, including heavy rainfalls, have an impact on pathogen transmission, also for Giardia

38 Shellfish Giardia in foodstuffs Vegetables Fruits Elute cysts from food surfaces Concentrate cysts by IMS Detect cysts by epifluorescence microscopy Giardia EPIDEMIOLOGY

39 Foodborne giardiasis No. of persons affected Suspected food-stuff Probable / possible source Christmas pudding home-canned salmon noodle salad rodent faeces food-handler food-handler sandwiches - fruit salad tripe soup ice raw sliced vegetables food-handler infected sheep food-handler food-handler We don t know much about the role of food Outbreaks are difficult to investigate EPIDEMIOLOGY

40 Clinical manifestations of giardiasis Very variable. Three situations can be distinguished: Asymptomatic giardiasis: this represents a considerable percentage of infections. The role of carriers in the epidemiology of giardiasis is not well understood Symptomatic giardiasis: the most common symptom is diarrhea, followed by nausea and abdominal pain. In severe cases, a malabsorption syndrome can occur Chronic giardiasis: in a smaller number of cases, the infection tends to be chronic, and can also be resistant to treatment DISEASE

41 Mechanisms of pathogenesis Molecules are excreted by the trophozoites upon contact with epithelial cells The parasite can evade the host immune response by replacing the VSP that covers the surface of the trophozoites The parasite can induce apoptosis and damage to epithelial cells Do assemblages/ genotypes differ with respect to these mechanisms? DISEASE

42 Correlation Giardia and symptoms Some studies have supported an association between assemblage A and symptoms (India, Australia, Turkey, Spain) On the contrary, other studies have reported an association with assemblage B and symptoms (Netherlands, Malaysia, Bangladesh, Ethiopia) And others found no correlation at all.. Still a very controversial aspect Studies were based on different sampling strategies, used different definition of symptoms, enrolled either children or adults or both, and have tested or not for the presence of other pathogens. DISEASE

43 Not a pathogen? This Ducth study showed that the prevalence (and DNA load) of Giardia is essentially the same in cases versus controls. Thus, the question of the pathogenicity of Giardia remains controversial. DISEASE

44 Giardia may be no more than a component of the intestinal microbiome, with a role or function of which we are currently not fully aware, but may include competing with other pathogens (Tysnes et al Trends Parasitol 214) Knowledge of the factors involved in determining the outcome of infection is essential. Should we look for complex interactions with the gut microbiota? Can we use this information to predict the outcome of infection? DISEASE

45 Treatment The drug of choice is metrinidazole. The drug is active against the trophozite but not the cyst. Cure rate 8-95%. Side effects include gastrointestinal pain and diarrhea, headache, vomiting, metallic taste In about 1-2% of patients, the treament is not effective TREATMENT

46 Drug «resistance» Giardia strains resistant to metronidazole have been isolated from patients or induced in vitro by drug exposure The resistance, an adaptive phenomenon dissimilar to classical resistance mechanisms, may involve: 1. Reduction of cellular permeability 2. Reduction in the activities of key enzymes that activate the drug 3. Use of alternative metabolic pathways 4. Changes in gene expression (chaperonine, variant surface proteins, etc.) 5. Expression of gene involved in stress resistance It follows that we can not predict Giardia drug resistance with a genetic-based test TREATMENT

47 To sum up Giardiasis is a very common infection in Europe, and globally Giardiasis is mainly a pediatric infection There are many transmission routes Waterborne outbreaks can be large Foodborne giardiasis is poorly understood Zoonotic transmission is not relevant We still don t know why only a fraction of infection is symptomatic Treatmet options are limited and drug resistance is an issue

48 We are now in the «omics» era The genomes of representative of Giardia duodenalis assemblage A (WB), ass. B (GS) and ass. E (P15) have been sequenced. Information from transcriptomics and proteomics studies is also available Information is stored at the EUPATHDB (Eukaryotic Pathogens) database The interaction of pathogens and the gut microbiota can now be approached using NGS technologies PERSPECTIVE

49 Thank you for your attention! Questions?