Encystment <Emphasis Type="Italic">in vitro</Emphasis> of the Cercariae <Emphasis Type="Italic">Himasthla elongata</Emphasis> (Trematoda: Echinostomatidae)

Trigger and toxic effects of Mytilus edulis (Bivalvia) hemolymph on encystment of cercariae Himasthla elongata obtained from infestated Littorina littorea (Prosobranchia) was evaluated as a result of 24-h experiments in vitro. The contact of H. elongata larvae with the whole hemolymph or mussel acellular plasma led to an intensive transformation of cercariae into metacercariae. In both tested media, the cercariae had to complete the encystment phase as fast as for 2 h, otherwise the risk of the larvae injury by humoral and cellular components of the mussel hemolymph would increase dramatically. The cercaria mortality after 24 h in the whole hemolymph was twice higher than in plasma (40% and 20%, respectively) and much higher than in the control medium (sea water). Both toxic and trigger effects of plasma was revealed to depend on its concentration, with the maximal larva mortality in the undiluted medium and with the highest number of successful transformations in the medium diluted more than 4 times. There is shown both the strong individual variability of toxicity of the individual mussel hemolymph for cercariae and the variability of the resistance to the toxic factors of the cercariae obtained from various L. littorea individuals. These experiments not only offer a method of the massive encystment of H. elongata cercariae, but also propose a perspective model for the study of the systemic defensive response of Bivalvia to invasion of multicellular parasite.     

Incidence of <Emphasis Type="Italic">Wolbachia</Emphasis> and <Emphasis Type="Italic">Cardinium</Emphasis> endosymbionts in the <Emphasis Type="Italic">Osmia</Emphasis> community in Korea

Sex ratio distorting endosymbionts induce reproductive anomalies in their arthropod hosts. They have recently been paid much attention as firstly texts of evolution of host-symbiont relationships and secondly potential biological control agents to control arthropod pests. Among such organisms, Wolbachia and Cardinium bacteria are well characterized. This study aims at probing such bacteria in the Osmia community to evaluate their potential utilization to control arthropod pests. Among 17 PCR tested species, Osmia cornifrons and a parasitic fly are infected with Wolbachia and a mite species is infected with Cardinium. Phylogenetic tree analyses suggest that horizontal transfer of the bacteria occurred between phylogenetically distant hosts.     

<Emphasis Type="Italic">Trichobilharzia regenti</Emphasis>: Antigenic structures of intravertebrate stages

Like several other bird schistosomes, neurotropic schistosome of Trichobilharzia regenti can invade also mammals, including humans. Repeated infections cause cercarial dermatitis, a skin inflammatory reaction leading to parasite elimination in non-specific mammalian hosts. However, in experimentally primo-infected mice, the worms escape from the skin and migrate to the central nervous system. In order to evade host immune reactions, schistosomes undergo cercaria/schistosomulum transformation accompanied with changes of surface antigens. The present study is focused on localization of the main antigens of T. regenti; cercariae, schistosomula developed under different conditions and adults were compared. Antigens were localized by immunofluorescence and ultrastructural immunocytochemistry using sera of mice repeatedly infected with T. regenti. Detected antibody targets were located in glycocalyx and penetration glands of cercariae and in tegument of cercariae, schistosomula and adults. Shedding of cercarial glycocalyx significantly reduced surface reactivity; further decrease was reported during ongoing development of schistosomula. Spherical bodies, probably transported from subtegumental cell bodies to worm surface, were identified as the most reactive tegumental structures. Based on similar results for schistosomula developed in specific, non-specific hosts and in vitro, it seems that the ability of T. regenti to decrease the surface immunoreactivity during ontogenesis is independent on the host type.     

Cytoplasmic incompatibility involving <Emphasis Type="Italic">Cardinium</Emphasis> and <Emphasis Type="Italic">Wolbachia</Emphasis> in the white-backed planthopper <Emphasis Type="Italic">Sogatella furcifera</Emphasis> (Hemiptera: Delphacidae)

Cytoplasmic incompatibility (CI) is a reproductive phenotype induced by bacterial endosymbionts in arthropods. Measured as a reduction in egg hatchability resulting from the crossing of uninfected females with bacteria-infected males, CI increases the frequency of bacteria-infected hosts by restricting the fertilization opportunities of uninfected hosts in populations. Wolbachia, a type of alpha-proteobacteria, is well known as a CI inducer in a wide range of arthropod species, while Cardinium, a member of the phylum Bacteroidetes, is known to cause CI in one wasp and three spider mite species. In this study, dual infection with Cardinium and Wolbachia induced strong CI in a single host, Sogatella furcifera (Horváth), a planthopper species that is naturally infected with both bacteria. Specifically, infection with Cardinium alone was found to cause a 76 % reduction in egg development, and dual infection with Cardinium and Wolbachia a 96 % reduction, indicating that Cardinium induces CI and the dual infection raises the CI level. This study was the first to document reproductive alteration by Cardinium in a diploid host species.     

Associations Between Coinfection Prevalence of <Emphasis Type="Italic">Borrelia lusitaniae</Emphasis>, <Emphasis Type="Italic">Anaplasma</Emphasis> sp., and <Emphasis Type="Italic">Rickettsia</Emphasis> sp. in Hard Ticks Feeding on Reptile Hosts

An increasing number of studies reveal that ticks and their hosts are infected with multiple pathogens, suggesting that coinfection might be frequent for both vectors and wild reservoir hosts. Whereas the examination of associations between coinfecting pathogen agents in natural host–vector–pathogen systems is a prerequisite for a better understanding of disease maintenance and transmission, the associations between pathogens within vectors or hosts are seldom explicitly examined. We examined the prevalence of pathogen agents and the patterns of associations between them under natural conditions, using a previously unexamined host–vector–pathogen system—green lizards Lacerta viridis, hard ticks Ixodes ricinus, and Borrelia, Anaplasma, and Rickettsia pathogens. We found that immature ticks infesting a temperate lizard species in Central Europe were infected with multiple pathogens. Considering I. ricinus nymphs and larvae, the prevalence of Anaplasma, Borrelia, and Rickettsia was 13.1% and 8.7%, 12.8% and 1.3%, and 4.5% and 2.7%, respectively. The patterns of pathogen prevalence and observed coinfection rates suggest that the risk of tick infection with one pathogen is not independent of other pathogens. Our results indicate that Anaplasma can play a role in suppressing the transmission of Borrelia to tick vectors. Overall, however, positive effects of Borrelia on Anaplasma seem to prevail as judged by higher-than-expected Borrelia–Anaplasma coinfection rates.     

Expression patterns of <Emphasis Type="Italic">engrailed</Emphasis> and <Emphasis Type="Italic">dpp</Emphasis> in the gastropod <Emphasis Type="Italic">Lymnaea stagnalis</Emphasis>

We isolated the full-length cDNAs of engrailed and dpp-BMP2/4 orthologues from the pond snail Lymnaea stagnalis and examined their expression patterns during development by the whole mount in situ hybridization. At the gastrula and trochophore stages, engrailed is expressed in the peripheral ectoderm of the presumptive and invaginating shell gland, corroborating its role in the shell formation that is widely conserved among molluscs. At the same stages, dpp-BMP2/4 is expressed in the right-hand side ectoderm of the shell gland and in the invaginating stomodaeum. Unlike in the gastropod Patella vulgata, our results suggested that dpp-BMP2/4 has a role in the shell formation, rather than in the regional specification and that it could be involved in the specification pathway of the left–right asymmetry of the developing shell in L. stagnalis.     

<Emphasis Type="Italic">Taenia arctos</Emphasis> n. sp. (Cestoda: Cyclophyllidea: Taeniidae) from its definitive (brown bear <Emphasis Type="Italic">Ursus arctos</Emphasis> Linnaeus) and intermediate (moose/elk <Emphasis Type="Italic">Alces</Emphasis> spp.) hosts

Taenia arctos n. sp. (Cestoda: Cyclophyllidea: Taeniidae) is described from the brown bear Ursus arctos Linnaeus (definitive host) and moose/elk Alces spp. (intermediate hosts) from Finland (type-locality) and Alaska, USA. The independent status of the new species and the conspecificity of its adults and metacestodes have been recently confirmed by the mtDNA sequence data of Lavikainen et al. (2011; Parasitology International, 60, 289–295). Special reference is given to morphological differences between the new species and T. krabbei Moniez, 1879 (definitive hosts primarily canines for the latter), both of which use the moose/elk (Alces spp.) as intermediate hosts (the latter also uses Rangifer and perhaps other northern ruminants), and between the new species and T. ursina Linstow, 1893, both of which use the brown bear U. arctos as a definitive host. New morphological data are also provided for adults and cysticerci of T. krabbei. The analysis includes potentially useful morphometric features that have not been previously applied to Taenia spp.     

The development of <Emphasis Type="Italic">Gymnophallus australis</Emphasis> Szidat, 1962 (Digenea: Gymnophallidae) from the Patagonian coast (Argentina) from metacercaria to adult,with an amended diagnosis of <Emphasis Type="Italic">Gymnophallus</Emphasis> Odhner, 1905

Parvatrema australis (Szidat, 1962) Szidat, 1965 was described based on larval stages found in specimens of the mussel Mytilus edulis from the Buenos Aires Province, Argentina. Although Szidat later examined hundreds of mussels, this parasite has never been found again until now. In the present study, larval stages, including germinal sacs, found in mytilids from the Patagonian coast were identified as P. australis. Metacercariae were incubated in vitro at 39 degrees C in physiological solution for 18-20 hours, by which time 80% of the specimens had eggs. P. australis is redescribed, on the basis of infective metacercariae and adults obtained in the laboratory, and is reassigned to Gymnophallus Odhner, 1900, the genus in which it was originally described. The generic diagnosis of Gymnophallus is here amended to include as diagnostic characters the presence or absence of the lateral lips, the form and position of the vitellarium (compact or follicular) and the presence of a pars prostatica (i.e. prostatic cells open into proximal part of the ejaculatory duct). The validity of some characters (i.e. the presence of lateral lips of the oral sucker, the form of the vitellarium and excretory vesicle, the extent of the uterus) as diagnostic at the generic level within the family Gymnophallidae is discussed. It is proposed that the least unambiguous characters that can be used to distinguish gymnophallid genera include the position of the ovary, the presence of a ventral pit and a pars prostatica, and caecal diverticula.     

<Emphasis Type="Italic">Wolbachia</Emphasis> and bacteriophage WO-B density of <Emphasis Type="Italic">Wolbachia</Emphasis> a-infected <Emphasis Type="Italic">Aedes albopictus</Emphasis> mosquito

Wolbachia are maternally inherited symbiotic bacteria capable of inducing an extensive range of reproductive abnormalities in their hosts, including cytoplasmic incompatibility (CI). Its density (concentration) is likely to influence the penetrance of CI in incompatible crosses. The variations of Wolbachia density could also be linked with phage WO density. We determined the relative density (relative concentration) of prophage WO orf7 and Wolbachia (phage-to-bacteria ratio) during early developmental and adult stages of singly infected Aedes albopictus mosquito (Wolbachia A-infected) by using real-time quantitative PCR. Phage WO and Wolbachia did not develop at the same rate. Relative Wolbachia density (bacteria-to-host ratio) was high later in development (adult stages) whilst relative prophage WO density (phage-to-bacteria ratio) was low in the adult stages. Furthermore, 12-d-old adults of singly infected female mosquito had the highest Wolbachia density. In contrast, the larval stage 4 (L4) contained the highest prophage WO-B orf7 density. The association of hosts-Wolbachia-phage among diverse species is different. Thus, if phage and Wolbachia are involved in CI mechanism, the information of this association should be acquired for each specific type of organism for future use of population replacement or gene drive system.     

Molecular dissection of <Emphasis Type="Italic">Bombyx mori</Emphasis> nucleopolyhedrovirus <Emphasis Type="Italic">orf8</Emphasis> gene

Viruses including baculoviruses are obligatory parasites, as their genomes do not encode all the proteins required for replication. Therefore, viruses have evolved to exploit the behavior and the physiology of their hosts and often coevolved with their hosts over millions of years. Recent comparative analyses of complete genome sequences of baculoviruses revealed the patterns of gene acquisitions and losses that have occurred during baculovirus evolution. In addition, knowledge of virus genes has also provided understanding of the mechanism of baculovirus infection including replication, species-specific virulence and host range. The Bm8 gene of Bombyx mori nucleopolyhedrovirus (NPV) and its homologues are found only in group I NPV genomes. The Autographa californica NPV Ac16 gene is a homologue of Bm8 and, encodes a viral structural protein. It has been shown that Bm8/Ac16 interacts with baculoviral and cellular proteins. Bm8/Ac16 interacts with baculoviral IE1 that is facilitated by coiled coil domains, and the interaction with IE1 is important for Bm8 function. Ac16 also forms a complex with viral FP25 and cellular actin and associates with membranes via palmitoylation. These data suggested that this gene family encodes a multifunctional protein that accomplishes specific needs of group I NPVs.      

The ectomycorrhizae of <Emphasis Type="Italic">Lactarius rimosellus</Emphasis> and <Emphasis Type="Italic">Lactarius acatlanensis</Emphasis> with the endangered <Emphasis Type="Italic">Fagus grandifolia</Emphasis> var. <Emphasis Type="Italic">mexicana</Emphasis>

Gut bacterium Pantoea sp. is one of the predominant bacterial species in the larval gut of the diamondback moth, Plutella xylostella. The phenotypic characters of Pantoea sp. were investigated with BIOLOG phenotype MicroArray (PM) in this study. Totally 950 different metabolic phenotypes were tested using the PM plates 1–10. Results exhibited that Pantoea sp. was able to metabolize 37.37 % of the tested carbon sources, 91.32 % of nitrogen sources, 100 % of sulfur sources, and 98.31 % of phosphorus sources. Most informative utilization patterns for carbon sources of Pantoea sp. were organic acids and carbohydrates, and for nitrogen were various amino acids. The bacterium had 94 different biosynthetic pathways. It had a wide range of adaptabilities, and could still metabolize in osmolytes with up to 9 % sodium chloride, 6 % potassium chloride, 5 % sodium sulfate, 20 % ethylene glycol, 4 % sodium formate, 4 % urea, 5 % sodium lactate, 200 mmol/L sodium phosphate (pH 7.0), 100 mmol/L ammonium sulfate (pH 8.0), 100 mmol/L sodium nitrate, and 100 mmol/L sodium nitrite, respectively. It also exhibited active metabolism under pH values between 4.5 and 10. Pantoea sp. showed active decarboxylase activities while poor deaminase activities in the presence of various amino acids. The phenotypic characterization of Pantoea sp. increased our knowledge of the bacterium, in particular its interactions with insect hosts and the adaptability in gut environments, and showed us some possible approaches to controlling diamondback moth through decreasing Pantoea sp. density.     

Clinical infection in house rats (<Emphasis Type="Italic">Rattus rattus</Emphasis>) caused by <Emphasis Type="Italic">Streptobacillus notomytis</Emphasis>

Rat bite fever is an under-reported, under-diagnosed emerging zoonosis with worldwide distribution. Besides Spirillum minus, Streptobacillus moniliformis is the major causative microorganism although it usually colonises rats without any clinical signs. A group of house rats (Rattus rattus) kept in a zoo exhibition for educational purposes suffered from neurological signs including disorientation, torticollis, stall walking, ataxia and death. Gross pathological and histo-pathological examinations of the investigated rats revealed high-grade otitis interna et media, from which Streptobacillus notomytis was isolated in pure culture or as the predominant microorganism. This case series underlines a previously expressed hypothesis that R. rattus might be naturally colonised with S. notomytis, whereas the traditional rat bite fever organism, S. moniliformis, might be restricted to the Norway rat (Rattus norvegicus). However, the general paucity of Streptobacillus isolates, especially from their respective animal hosts, precludes definitive proof of these host tropisms. This is the first report of S. notomytis detection outside Asia and Australia and the first evidence for its role as a facultative pathogen in house rats.     

Detection of <Emphasis Type="Italic">Candida</Emphasis><Emphasis Type="Italic">dubliniensis</Emphasis> in Venezuela

Over the past decades there has been a significant increase in fungal infections caused by Candida species, and continues to be common in immunocompromised individuals infected with the human immunodeficiency virus (HIV). Although Candida albicans remains the fungal species most frequently isolated as an opportunistic oral pathogen, other non-albicans are often identified in this cohort of patients, including C. dubliniensis. This yeast is closely related to and shares many phenotypic characteristics with C. albicans. Colonies of these two species appear morphologically identical when not grown on special media. The shared phenotypic characteristics of C. dubliniensis and C. albicans suggest that many C. dubliniensis isolates may have been misidentified as C. albicans in the past. The present studies aim is to recover and identify C. dubliniensis, and presumptive clinical C. albicans, from the oral cavities of HIV-seropositive individuals, comparing conventional media to obtain a simple, low-cost and reliable identification system for C. dubliniensis. A total of 16 isolates (3,98%) had been obtained from 402 HIV infected individuals with recurrent oropharyngitis and were identified as C. dubliniensis. Out of these C. dubliniensis isolates 19% were resistant, with MICs above 64 μg/ml to fluconazole. This constitutes, to the authors knowledge the first recovery of this organism in Venezuela.     

<Emphasis Type="Italic">Corynosoma australe</Emphasis> Johnston, 1937 and <Emphasis Type="Italic">C. cetaceum</Emphasis> Johnston &; Best, 1942 (Acanthocephala: Polymorphidae) from marine mammals and fishes in Argentinian waters: allozyme markers and taxonomic status

Genetic and morphological studies were carried out on acanthocephalans belonging to Corynosoma Lühe, 1904 and referable to the species C. cetaceum Johnston & Best, 1942 and C. australe Johnston, 1937, which were recovered from both definitive and intermediate hosts in Argentinian waters. The aims were to estimate the level of genetic differentiation between the two taxa at any stage of their life-cycle, to provide genetic (allozyme) markers for their recognition and to analyse the systematic status of both taxa. Acanthocephalans were collected from the stomach and intestine of Arctocephalus australis (Zimmerman), the intestine of Mirounga leonina (Linnaeus) and the stomach of Pontoporia blainvillei Gervais & D’Orbigny (definitive hosts) in Argentinian waters. Alternative alleles at all the 13 enzymatic loci studied were observed for C. australe and C. cetaceum. The specimens from the stomach of both P. blainvillei and A. australis were identified, on the basis of the great number of diagnostic loci found, as C. cetaceum; those from intestine of both A. australis and M. leonina as C. australe. A high level of genetic differentiation (D_Nei=∞: I_Nei = 0.00) between the two taxa was found, suggesting a generic distinction between the two species. Cystacanths of the two species from the body-cavity of the fish Cynoscion guatucupa (Cuvier) collected from the same geographical area were identified genetically. Morphological patterns, such as the number of hooks and hook rows on the proboscis, the distribution of somatic and genital armature, and other morphometric and meristic differences, in addition to ecological data, enabled the identification of these two species at cystacanth, juvenile and adult stages. However, a number of morphological and morphometric features of the Argentinian material were different to those of C. australe and C. cetaceum described from other regions of the world.     

Methylmercury levels in a parasite (<Emphasis Type="Italic">Apophallus brevis</Emphasis> metacercariae) and its host,yellow perch (<Emphasis Type="Italic">Perca flavescens</Emphasis>)

The biomagnification of methylmercury (MeHg) amongst trophic levels results in high levels of this compound in many freshwater fish species. The role of parasites in MeHg cycling and trophic transfer in freshwater systems is largely unknown. This study examined the potential for metacercariae of Apophallus brevis to accumulate and biomagnify MeHg from their second intermediate host, yellow perch, Perca flavescens. Contrary to our prediction that MeHg levels would be higher in parasites than in the host muscle tissue in which they are embedded, we found that concentrations were similar. The lack of increase in MeHg levels from host to parasite may be due to limited assimilation of host muscle tissue or, in part, to low parasite metabolism. Parasite load did not reduce fish growth and subsequently alter MeHg concentrations. This study suggests that relationships between larval parasites and their hosts do not conform to typical patterns of MeHg biomagnification seen in aquatic systems.     

<Emphasis Type="Italic">Aeromonas salmonicida</Emphasis> infected fish transfer disease to healthy fish <Emphasis Type="Italic">via</Emphasis> water

Experimental studies of infection transmission via water from infected to healthy fish were conducted. The dark-brown bacterial colonies typical for Aeromonas salmonicida on tryptone soya agar (TSA) have been isolated and counted (from 3.0±0.6×10² to 3.5±0.5×10⁵ c.f.u. g⁻¹) from the internal organs of naturally infected (NI) and experimentally infected (EI) perch and sea trout. No significant differences in dark-brown bacterial counts were detected between EI perch and EI sea trout. The assessment and comparison of the alterations of the biological parameters of EI European perch and sea trout with bacterium Aeromonas salmonicida subsp. salmonicida with naturally infected perch were conducted. No mortality was recorded in groups of EI perch and sea trout. Whereas, the mortality of NI perch (collected from the main sites of outbreak of disease) was observed from the second day of the experiments. Changes in morphophysiological parameters of EI perch and sea trout were similar. Different alterations in blood cell parameters of EI fish were observed, and the most noticeable was the decrease (P≤0.01) in white blood cell count (WBC) of EI perch and sea trout. Based on these results it can be deduced that there is infection transmission of bacterium A. salmonicida from European perch via water to other fish species.     

Male-killing <Emphasis Type="Italic">Wolbachia</Emphasis> do not protect <Emphasis Type="Italic">Drosophila bifasciata</Emphasis>against viral infection

BACKGROUND: Insect symbionts employ multiple strategies to enhance their spread through populations, and some play a dual role as both a mutualist and a reproductive manipulator. It has recently been found that this is the case for some strains of Wolbachia, which both cause cytoplasmic incompatibility and protect their hosts against viruses. Here, we carry out the first test as to whether a male-killing strain of Wolbachia also provides a direct benefit to its host by providing antiviral protection to its host Drosophila bifasciata. We infected flies with two positive sense RNA viruses known to replicate in a range of Drosophila species (Drosophila C virus and Flock House virus) and measure the rate of death in Wolbachia positive and negative host lines with the same genetic background. RESULTS: Both viruses caused considerable mortality to D. bifasciata flies, with Drosophila C virus killing 43% more flies than the uninfected controls and Flock House virus killing 78% more flies than the uninfected controls. However, viral induced mortality was unaffected by the presence of Wolbachia. CONCLUSION: In the first male-killing Wolbachia strain tested for antiviral effects, we found no evidence that it conferred protection against two RNA viruses. We show that although antiviral resistance is widespread across the Wolbachia phylogeny, the trait seems to have been lost or gained along some lineages. We discuss the potential mechanisms of this, and can seemingly discount protection against these viruses as a reason why this symbiont has spread through Drosophila populations.     

Influence of different host associations on glutamine synthetase activity and ammonium transporter in <Emphasis Type="Italic">Santalum</Emphasis><Emphasis Type="Italic">album</Emphasis> L.

The present study was aimed at understanding the role of different hosts in ammonium transporter1;2 expressions and glutamine synthetase(GS) activity and their effects on the growth parameters in the sandal. Sandal plant associated with leguminous host expressed better growth parameters. GS activity of leguminous hosts alone and in host associated sandals was analyzed using GS transferase assay. Highest GS activity was expressed in Mimosa pudica—sandal association compared to other leguminous and non-leguminous host associations. The association of N₂ fixing host with sandal enhanced C and N levels in order to maintain the C/N value. The role of ammonium transporters in N nutrition of sandal-host association was elucidated by cloning AMT1;2 from the leaves, haustoria and roots of host associated sandal and quantifying the relative expression by the \( 2^{{ - \Delta \Delta {\text{C}}_{\text{T}} }} \) method. SaAMT1;2 was strongly up-regulated in leaves, roots and haustoria of leguminous host associated sandal compared to non-leguminous host associations. The relative increase in SaAMT1;2 expressions and up-regulated GS activity positively affected the growth parameters in sandal when associated with leguminous hosts.     

Phenotypic Switching of <Emphasis Type="Italic">Cryptococcus neoformans</Emphasis> and <Emphasis Type="Italic">Cryptococcus</Emphasis><Emphasis Type="Italic">gattii</Emphasis>

Microorganisms that live in fluctuating environments must constantly adapt their behavior to survive. The host constitutes an important microenvironment in opportunistic and primary fungal pathogens like Cryptococcus neoformans (C. neoformans) and Cryptococcus gattii (C. gattii). In clonal populations, adaptation may be achieved through the generation of diversity. For fungi phenotype switching constitutes a mechanism that allows them to change rapidly. Both C. neoformans and C. gattii undergo phenotypic switching, which allows them to be successful pathogens and cause persistent disease. Similar to other encapsulated microbes that exhibit phenotypic variation, phenotypic switching in Cryptococcus changes the polysaccharide capsule. Most importantly, in animal models phenotypic switching affects virulence and can change the outcome of infection. Virulence changes because C. neoformans and C. gattii switch variants elicit different inflammatory responses in the host. This altered host response can also affect the response to antifungal therapy and in some cases may even promote the selection of switch variants. This review highlights the similarity and differences between phenotypic switching in C. neoformans and C. gattii, the two dominant species that cause cryptococcosis in humans.