Use In Disease Control Research Articles

Impact of Xpert MTB/RIF implementation in tuberculosis case detection and control in Brazil: a nationwide intervention time-series analysis (2011–2022)

Since 2014, Brazil has gradually implemented the Xpert MTB/RIF (Xpert) test to enhance early tuberculosis (TB) and drug-resistant (DR-TB) detection and control, yet its nationwide impact remains underexplored. Our study conducts an intervention time-series analysis (ITSA) to evaluate how the Xpert's implementation has improved TB and DR-TB detection nationwide. 1,061,776 cases from Brazil's National TB Registry (2011-2022) were reviewed and ITSA (2011-2019) was used to gauge the impact of the Xpert's adoption on TB and DR-TB notification. Granger Causality and dynamic regression modelling determined if incorporating Xpert testing as an external regressor enhanced forecasting accuracy for Brazil's future TB trends. Xpert implementation resulted in a 9.7% increase in TB notification and substantial improvements in DR-TB (63.6%) and drug-susceptible TB (92.1%) detection compared to expected notifications if it had not been implemented. Xpert testing counts also presented a time-dependent relationship with DR-TB detection post-implementation, and improved predictions in forecasting models, which depicted a potential increase in TB and DR-TB detection in the next six years. This study underscores the critical role of Xpert's adoption in boosting TB and DR-TB detection in Brazil, reinforcing the case for its widespread use in disease control. Improvements in prediction accuracy resulting from integrating Xpert data are crucial for allocating resources and reducing the incidence of TB. By acknowledging Xpert's role in both disease control and improving predictions, we advocate for its expanded use and further research into advanced molecular diagnostics for effective TB and DR-TB control. FIOCRUZ.

Phytotherapy use for disease control in aquaculture: a review of the last 5 years

Phytotherapy use for disease control in aquaculture: a review of the last 5 years

Biology and Transmission Dynamics of Aedes flavivirus.

Aedes albopictus (Skuse) and Aedes aegypti (Linnaeus) (Diptera: Culicidae) mosquitoes transmit pathogenic arthropod-borne viruses, including dengue, chikungunya, and Zika viruses, with significant global health consequences. Both Ae. albopictus and Ae. aegypti also are susceptible to Aedes flavivirus (AEFV), an insect-specific flavivirus (ISF) first isolated in Japan from Ae. albopictus and Ae. flavopictus. ISFs infect only insect hosts and evidence suggests that they are maintained by vertical transmission. In some cases, ISFs interfere with pathogenic flavivirus infection, and may have potential use in disease control. We explored the host range of AEFV in 4 genera of mosquitoes after intrathoracic injection and observed greater than 95% prevalence in the species of Aedes and Toxorhynchites tested. Anopheles and Culex species were less permissive to infection. Vertical transmission studies revealed 100% transovarial transmission and a filial infection rate of 100% for AEFV in a persistently-infected colony of Ae. albopictus. Horizontal transmission potential was assessed for adult and larval mosquitoes following per os exposures and in venereal transmission experiments. No mosquitoes tested positive for AEFV infection after blood feeding, and infection with AEFV after sucrose feeding was rare. Similarly, 2% of adult mosquitoes tested positive for AEFV after feeding on infected cells in culture as larvae. Venereal transmission of AEFV was most frequently observed from infected males to uninfected females as compared with transmission from infected females to uninfected males. These results reveal new information on the infection potential of AEFV in mosquitoes and expand our understanding of both vertical and horizontal transmission of ISFs.

Nanotechnology in veterinary medicine: a review

ABSTRACT: The purpose of this review was to address the applicability of nanotechnology in veterinary medicine, with an emphasis on research in Brazil from 2013 to 2020. Firstly, we introduced to the general aspects of applicability of nanotechnology in veterinary medicine, and lately we pointed the research involving nanoscience performed in Brazil, in the studied period. Nanotechnology is the field of science that has the capacity to organize matter in nanoscale structures (1 to 100 nm), enabling innovations in different areas including biotechnology, agriculture, disease diagnosis, food and clothing industry, electronics, and pharmacological therapies. In veterinary medicine, several studies are being carried out in the world, mainly in the areas that involve search of new treatment options and the development of immunotherapy, as well as in the diagnosis of diseases. In Brazil, it is clear that the use of nanotechnology in veterinary medicine is still incipient, but it can be considered a growing area. In addition, several points have to be reflected and researched, including some adverse effects and implications to validate the safe use of nanotechnology in veterinary medicine. Therefore, this review highlighted the nanotechnology as a promise alternative in the current context of Brazilian technological innovation involving animal health, as well as a possible diagnostic tool and highlighting its potential therapeutic use in disease control in veterinary medicine. Regarding future perspectives, we believed that greater investment in science and technology could contribute to the advancement and strengthening of nanotechnology in Brazil.

Effects of antibiotic treatment on antimicrobial resistance in pig microbiomes: a longitudinal study

Abstract The United Kingdom has prohibited the prophylactic use of antibiotics in agriculture but they are still critical for disease control. It is thus vital to understand the effects of antibiotic treatment on antimicrobial resistance (AMR) spread. Hi-C metagenomic sequencing can help identify AMR genes in animal microbiomes and assign plasmid-based genes to their bacterial hosts. Leveraging Hi-C, we sequence antibiotically-treated pig microbiomes through time to identify dynamic trends in AMR gene prevalence. Fecal samples were collected at time points prior to and following antibiotic treatment in 6 farms across England when pigs presented with illness. Control samples were collected from 2 of these farms at multiple time points without treatment. Samples were processed using a bioinformatic pipeline that outputs assemblies with information on taxonomic classification and presence/absence of an AMR allele. 115 AMR alleles across 11 antibiotic classes were included. The bacterial species in highest abundance/farm belonged to order Bacteroidales (45.9-53.1%). Tetracycline resistance alleles showed the highest prevalence/farm (28.4-52.8%). No significant association between bacterial species abundance and time point, and AMR allele prevalence and time point was found in all farms (χ2 p>.05). The distribution of the number of AMR alleles/assembly was significantly higher between the first and last time point in 4/6 treated farms and 1/2 control farms (Wilcoxan rank sum p <.01). A higher difference in the proportion of assemblies with greater than 6 AMR alleles between the first and last time point was observed in 1 treated farm (.17 95% CI .013-.21) compared to its control (.03 95% CI .023-.033). Slight acquisition of AMR alleles was observed but we see minimal temporal fluctuations in bacterial species abundance and AMR allele prevalence overall implying that the microbiome is fairly robust to antibiotic treatment. This encourages its responsible use for disease control. Key messages Ensuring that the responsible use of antibiotics does not drastically affect AMR mobilization is key to preserving the efficacy of therapeutics in agriculture. While acquisition of resistance genes over time is seen it cannot conclusively be tied to treatment; Minimal microbiome perturbation post treatment implies that therapeutic antibiotic use is warranted.

In vivo praziquantel efficacy of Schistosoma japonicum over time: A systematic review and meta-analysis

Praziquantel (PZQ), the only choice of chemotherapy for schistosomiasis recommended by World Health Organization (WHO), has been widely used over 40 years. The long-term, and rapid expansion of, PZQ use for disease control across a large populations continues to raise concern regarding the potential for emergence and establishment of drug resistance. Recent research has also proposed that the long survival and low sensitivity of unpaired worms, derived from either incomplete treatment cure rates or single-sex schistosome infections within final hosts, could exacerbate the risk of PZQ resistance (PZQ-R) emerging. With the aim of assessing whether PZQ efficacy amongst S. japonicum may have changed over time in China, we performed a unique systematic review and meta-analyses on datasets which evaluated the efficacy of PZQ via laboratory assays of field S. japonicum isolates on experimental mice over time. Relevant published literatures from four electronic bibliographic databases and lists of article references were searched. Two indexes, d, a measure used in meta-analyses for worm burden difference between two groups, and r, a traditional measure for worm reduction percentage after treatment but without considering sample size were calculated for each study. A total of 25 papers including 127 experimental studies with eligible data on 2230 mice were retrieved. The pooled d (D) was 3.91 (3.56–4.25) and pooled r (R) was 54.52% (52.55%–56.52%). D significantly increased over time, whereas R non-significantly decreased; both estimates were significantly associated with the total drug dose. Such findings suggested no evidence of PZQ-R emergence S. japonicum to date. However, we consider the potential role of parasite origins, PZQ dosage, and single versus mixed gender infections of the results published to date, and the avenues now needed for further research.

Is Galanin a Promising Therapeutic Resource for Neural and Nonneural Diseases?

Galanin (GAL) constitutes a family of neuropeptides composed of four peptides: (i) galanin (GAL), (ii) galanin-message associated peptide (GAMP), (iii) galanin-like peptide (GALP), and (iv) alarin. GAL contains 29/30 amino acids, and its biological action occurs through the interactions with its various receptors (GALR1, GALR2, and GALR3). The neuropeptide GAL regulates several physiological and pathophysiological functions in the central nervous system, the peripheral nervous system, and the peripheral organs. GAL is secreted mainly by oligodendrocytes, astrocytes, and the gastrointestinal tract, and its effect depends on the interaction with its different receptors. These receptors are expressed mainly in the central, peripheral nervous systems and the intestines. The present review evaluates the role of GAL family in inflammatory diseases. An overview is given of the signaling and pharmacological effects due to the interaction between GAL and GALR in different cell types. The potential use of GAL as a therapeutic resource is critically discussed. GAL is suggested to have an anti-inflammatory function in some situations and a proinflammatory function in others. The literature on GAL is controversial and currently not conclusive. This could be due to the complexity of the metabolic network signaling induced by the interactions between GAL and GALR. In the next future, GAL might be a promising therapeutic resource for several diseases, but its practical use for disease control is presently not advisable.

Characterization of a thermostable κ-carrageenase from a hot spring bacterium and plant protection activity of the oligosaccharide enzymolysis product.

Seaweed oligosaccharides are environmentally-friendly natural products and their use for disease control in sustainable agriculture is extremely promising. Enzymatic digestion to prepare seaweed oligosaccharides has drawn considerable interest. However, the study of enzymatically degraded products of carrageenan is still in its infancy compared with that of other hydrocolloids such as agar and alginate. To prepare degraded carrageenan on a commercial scale, it is necessary to select superior producer bacterial strains to improve the yield and thermostability of carrageenases. The carrageenan-degrading bacterium Bacillus sp. HT19 was isolated from sediment of a hot spring in Indonesia, and a κ-carrageenase with high activity was purified from the culture supernatant. The purified enzyme, named Car19, had maximum activity (538 U mg-1 ) at 60 °C and pH 7.0. Notably, the enzyme retained >90% of its initial activity after incubation at 60 °C for 24 h. The Ca2+ obviously improved the thermostability of Car19 at 70 °C. The Km and Vmax values of purified Car19 were 0.061 mg mL-1 and 115.13 U mg-1 , respectively, with κ-carrageenan as substrate. Thin-layer chromatography and electrospray ionization mass-spectrometry analysis of hydrolysates indicated that the enzyme exolytically depolymerized κ-carrageenan to neo-carrabiose. The hydrolysate enhanced the resistance of cucumber to cucumber mosaic virus and increased the activity of antioxidant enzymes in infected plants. To our knowledge, Car19 is the most thermostable κ-carrageenase reported so far. Its high optimal reaction temperature and thermostability, and unitary hydrolysate constituent, makes Car19 a promising candidate for the preparation of carrageenan oligosaccharides with plant protection activity. © 2018 Society of Chemical Industry.

Evaluation of ionic liquids supported on silica as a sorbent for fully automated online solid-phase extraction with LC-MS determination of sulfonamides in bovine milk samples.

Sulfonamides are antibiotics widely used in the treatment of diseases in dairy cattle. However, their indiscriminate use for disease control may lead to their presence in tissues and milk and their determination requires a sample preparation step as part of an analytical approach. Among the several sample preparation techniques available, those based upon the use of sorptive materials have been widely employed. Recently, the application of ionic liquids immobilized on silica surfaces or polymeric materials has been evaluated for such an application. This manuscript addresses the evaluation of silica-based ionic liquid obtained by a sol-gel synthesis process by basic catalysis as sorbent for online solid-phase extraction with liquid chromatography and electrospray ionization time-of-flight mass spectrometry for sulfonamides determination. Infrared vibrational spectroscopy confirmed the presence of the ionic liquid on the silica surface, suggesting that the ionic liquid was anchored on to the silica surface. Other sorbents varying the ionic liquid alkyl chain were also synthesized and evaluated by off-line solid-phase extraction in the sulfonamide extraction. As the length of the alkyl chain increased, the amount of extracted sulfonamides decreased, possibly due to a decrease in the electrostatic interaction caused by the reduction in the polarity, as well as the presence of a hexafluorophosphate anion that increases the hydrophobic character of the material. The use of 1-butyl-3-methylimidazolium hexafluorophosphate as a selective ionic liquid sorbent enabled the isolation and sulfonamide preconcentration in bovine milk by online solid-phase extraction with liquid chromatography and electrospray ionization time-of-flight mass spectrometry. The limit of quantification for the method developed was 5-7, 5 μg/mL, with extraction recoveries ranging between 74 and 93% and intra- and interassay between 1.5-12.5 and 2.3-13.1, respectively.

A potential application of shrimp antilipopolysaccharide factor in disease control in aquaculture

Antilipopolysaccharide factor isoform 3 from Penaeus monodon (ALFPm3) exhibits broad antimicrobial activities against various microbes, including bacteria, fungi and viruses, suggesting its potential use in disease control in shrimp aquaculture. Herein, the recombinant ALFPm3 protein (rALFPm3) exhibited effective antibacterial action against Vibrio parahaemolyticus, the causative agent of the new severe emerging disease, early mortality syndrome (EMS) or acute hepatopancreatic necrosis disease (AHPND) at the minimum inhibitory concentration value of 1.25–5.00 μM. The morphological changes such as bleb formation and cell distortion of V. parahaemoluticus were introduced after rALFPm3 treatment. Furthermore, to control V. parahaemoluticus infection, shrimp were treated with rALFPm3 by immersion and reduction in the cumulative mortality of V. parahaemoluticus-infected Penaeus vannamei was observed. As a potential immunostimulant, the administration of dietary rALFPm3 enhanced the transcript level of five immune-related genes; ALFPm3, haemocyte homoeostasis-associated protein, phagocytosis-activating protein, prophenoloxidase-activating enzyme 1 and cytosolic manganese superoxide dismutase. In addition, dietary rALFPm3 increased the shrimp survival after white spot syndrome virus (WSSV) injection by >35% compared to the 0% survival for the control group. Taken together, these results indicate the potential use of dietary rALFPm3 as immunostimulant in controlling AHPND and WSSV infections in shrimp aquaculture.

The effect of virus-blocking Wolbachia on male competitiveness of the dengue vector mosquito, Aedes aegypti.

BackgroundThe bacterial endosymbiont Wolbachia blocks the transmission of dengue virus by its vector mosquito Aedes aegypti, and is currently being evaluated for control of dengue outbreaks. Wolbachia induces cytoplasmic incompatibility (CI) that results in the developmental failure of offspring in the cross between Wolbachia-infected males and uninfected females. This increases the relative success of infected females in the population, thereby enhancing the spread of the beneficial bacterium. However, Wolbachia spread via CI will only be feasible if infected males are sufficiently competitive in obtaining a mate under field conditions. We tested the effect of Wolbachia on the competitiveness of A. aegypti males under semi-field conditions.Methodology/Principal FindingsIn a series of experiments we exposed uninfected females to Wolbachia-infected and uninfected males simultaneously. We scored the competitiveness of infected males according to the proportion of females producing non-viable eggs due to incompatibility. We found that infected males were equally successful to uninfected males in securing a mate within experimental tents and semi-field cages. This was true for males infected by the benign wMel Wolbachia strain, but also for males infected by the virulent wMelPop (popcorn) strain. By manipulating male size we found that larger males had a higher success than smaller underfed males in the semi-field cages, regardless of their infection status.Conclusions/SignificanceThe results indicate that Wolbachia infection does not reduce the competitiveness of A. aegypti males. Moreover, the body size effect suggests a potential advantage for lab-reared Wolbachia-males during a field release episode, due to their better nutrition and larger size. This may promote Wolbachia spread via CI in wild mosquito populations and underscores its potential use for disease control.

Evaluation of the long-lasting insecticidal net Interceptor LN: laboratory and experimental hut studies against anopheline and culicine mosquitoes in northeastern Tanzania

BackgroundLong lasting insecticidal nets (LN) are a primary method of malaria prevention. Before new types of LN are approved they need to meet quality and efficacy standards set by the WHO Pesticide Evaluation Scheme. The process of evaluation has three phases. In Phase I the candidate LN must meet threshold bioassay criteria after 20 standardized washes. In Phase II washed and unwashed LNs are evaluated in experimental huts against wild, free flying anopheline mosquitoes. In Phase III the LN are distributed to households in malaria endemic areas, sampled over three years of use and tested for continuing insecticidal efficacy. Interceptor® LN (BASF Corporation, Germany) is made of polyester netting coated with a wash resistant formulation of alpha-cypermethrin.MethodsInterceptor LN was subjected to bioassay evaluation and then to experimental hut trial against pyrethroid-susceptible Anopheles gambiae and An. funestus and resistant Culex quinquefasciatus. Mosquito mortality, blood feeding inhibition and personal protection were compared between untreated nets, conventional alpha-cypermethrin treated nets (CTN) washed 20 times and LNs washed 0, 20 and 30 times.ResultsIn Phase I Interceptor LN demonstrated superior wash resistance and efficacy to the CTN. In the Phase II hut trial the LN killed 92% of female An. gambiae when unwashed and 76% when washed 20 times; the CTN washed 20 times killed 44%. The LN out-performed the CTN in personal protection and blood-feeding inhibition. The trend for An. funestus was similar to An. gambiae for all outcomes. Few pyrethroid-resistant Cx. quinquefasciatus were killed and yet the level of personal protection (75-90%) against Culex was similar to that of susceptible An. gambiae (76-80%) even after 20 washes. This protection is relevant because Cx. quinquefasciatus is a vector of lymphatic filariasis in East Africa. After 20 washes and 60 nights’ use the LN retained 27% of its initial insecticide dose.ConclusionsInterceptor LN meets the approval criteria set by WHO and is recommended for use in disease control against East African vectors of malaria and filariasis. Some constraints associated with the phase II evaluation criteria, in particular the washing procedure, are critically reviewed.

Control of porcine reproductive and respiratory syndrome (PRRS) through genetic improvements in disease resistance and tolerance.

Infections caused by porcine reproductive and respiratory syndrome virus (PRRSV) have a severe economic impact on pig production in North America, Europe, and Asia. The emergence and eventual predominance of PRRS in the 1990s are the likely result of changes in the pork industry initiated in the late 1970s, which allowed the virus to occupy a unique niche within a modern commercial production system. PRRSV infection is responsible for severe clinical disease, but can maintain a life-long subclinical infection, as well as participate in several polymicrobial syndromes. Current vaccines lessen clinical signs, but are of limited use for disease control and elimination. The relatively poor protective immunity following vaccination is a function of the virus's capacity to generate a large degree of genetic diversity, combined with several strategies to evade innate and adaptive immune responses. In 2007, the PRRS Host Genetics consortium (PHGC) was established to explore the role of host genetics as an avenue for PRRS control. The PHGC model for PRRS incorporates the experimental infection of large numbers of growing pigs and has created the opportunity to study experimental PRRSV infection at the population level. The results show that pigs can be placed into distinct phenotypic groups, including pigs that show resistance (i.e., low virus load) or pigs that exhibit “tolerance” to infection. Tolerance was illustrated by pigs that gain weight normally in the face of a relatively high virus load. Genome-wide association analysis has identified a region on chromosome 4 (SSC4) correlated with resistance; i.e., lower cumulative virus load within the first 42 days of infection. The genomic region is near a family of genes involved in innate immunity. The region is also associated with higher weight gain in challenged pigs, suggesting that pigs with the resistance alleles don't seem to simultaneously experience reduction in growth, i.e., that resistance and tolerance are not antagonistically related. These results create the opportunity to develop breeding programs that will produce pigs with increased resistance to PRRS and simultaneously high growth rate. The identification of genomic markers involved in actual tolerance will likely prove more difficult, primarily because tolerance is difficult to quantify and because tolerance mechanism are still poorly understood. Another avenue of study includes the identification of genomic markers related to improved response following vaccination.

Invertebrate Post-Segregation Distorters: A New Embryo-Killing Gene

Cytoplasmic incompatibility induced by inherited intracellular bacteria of arthropods, and Medea elements found in flour beetles, are both forms of postsegregation distortion involving the killing of embryos in order to increase the ratio of progeny that inherit them. The recently described peel-zeel element of Caenorhabditis elegans also uses this mechanism; like Medea the genes responsible are in the nuclear genome but it shares a paternal mode of action with the bacteria. The peel-1 gene has now been shown to encode a potent toxin that is delivered by sperm, and rescued by zygotic transcription of the linked zeel-1. The predominance of self-fertilization in C. elegans has produced an unusual distribution pattern for a selfish genetic element; further population and functional studies will shed light on its evolution. The element might also have potential for use in disease control.

A Review of Alternative Practices to Antimicrobial Use for Disease Control in the Commercial Feedlot – Executive Summary

The purpose of the present review was two fold: to give an overview of the modern feedlot industry in North America to provide context, and to search the scientific literature to identify alternative practices for antimicrobial use for disease control in that same industry. A fundamental assumption of the review was that reducing antimicrobial use would reduce the potential for antimicrobial-resistant bacteria to emerge and persist in the feedlot setting. To most effectively reduce antimicrobial use in the feedlot, one needs to find alternatives to prevent or effectively manage bacterial pneumonia in calves (often the principle reason for antimicrobial use) around the time of their arrival at the feedlot, as well as other bacterial diseases (eg, liver abscesses). Therefore, our key review question was the following: Are there management practices that do not involve the administration of antimicrobials that reduce the incidence of illness and mortality due to pneumonia, especially in high-risk feedlot calves? To answer this question, we set out to document the known risk factors for the emergence and maintenance of antimicrobial resistance (AMR) on feedlots, and the critical control points for these risk factors. We sought evidence for the effectiveness, efficiency and/or acceptability of various infection control points in a feedlot setting. We questioned whether the metaphylactic use of antimicrobials would affect the emergence of resistant bacteria in a feedlot setting, and asked what impact, if any, different drug use implementation strategies (including rotation of drugs used within a feedlot) might have on AMR. We also searched for management practices that reduce the incidence of liver abscesses in feedlot cattle, but that do not rely on in-feed or subtherapeutic antimicrobial use.

Population-Level Interventions to Reduce the Development and Transmission of Community-Associated Antimicrobial Resistance: A Perspective from the National Collaborating Centre for Infectious Diseases

Antimicrobial resistance (AMR) in bacteria is the end result of a multitude of factors. Some of the key factors beyond innate resistance include antimicrobial selective pressure (1–5), acquisition of a foreign genetic resistance element(s) (1–5), clonal dissemination (1) and new mutations (2,3,5); factors vary for different species and geographical locations. Increased global antimicrobial use is the foremost reason for the spread of AMR in the community setting (1). Social networks of individuals (households, schools and child care facilities) have served both as a reservoir for these bacteria and as a common route for their transmission. Similarly, hospitals, nursing homes and long-term care facilities have also served as reservoirs for antibiotic-resistant organisms, and the discharge of patients from these facilities contributes to the spread of resistance within communities. In addition, the use of antimicrobials in food animals has been an important contributing cause (1).

DISTRIBUTION OF MERCURY RESIDUES FROM THE USE OF MERCURIAL FUNGICIDES ON GOLF COURSE GREENS

Soil samples taken from two golf courses with a long history of mercurial fungicide use for disease control showed mercury residues in excess of background levels to a maximum depth of 30 cm at one site and 60 cm at the other. Laterally, residues were found up to 30 m from the treated areas at both sides.

Water Relations of Water Molds

As a plant pathologist my definition of the water molds necessarily includes zoosporic fungi ranging all the way from truly aquatic, nonmycelial forms to completely terrestrial forms with well-developed mycelium (92). In other words, rather than confining the water molds to those Chytridiomycetes, Hypochytridiomycetesand Oomycetes that occur in fresh water, terrestrial and marine members of these classes are included. In fact, most of what we know about the water relations of water molds comes from research on their salt tolerance or parasitism of terrestrial plants. Notable in this regard are Phytophthora infestans and the downy mildews, for rudimentary knowledge of their water relations has facilitated disease forecasting and control [e.g. see references in (21, 84)]. The aerial environment oscillates between ex­ tremes of water status and, fortunately, the water requirements of P. infes­ tans and the downy mildews are satisfied only part of the time. Most of the substrates on which zoosporic fungi grow have a water status that is very much higher and more constant than the humidities of ambient air would' suggest, and for even closely related plant pathogens that inhabit soil, such as Phytophthora and Pythium species, the determination of permissive conditions for epidemic increase will be more difficult. Nevertheless, the literature and considerable field experience indicate that very wet soil condi­ tions enhance many Phytophthora and Pythium diseases (e.g. 17, 34, 36, 45, 93, 99; 117), and through more· r.esearch their water requirements may become sufficiently known for practical use in disease control and irrigation management. Even the most terrestrial examples of zoosporic fungi have not lost all aquatic affinities, and the response of zoosporic fungi to small changes in