Publications and Presentations

Thesis Research

Professional Activities

Brandon was involved in a wide variety of research projects studying mosquitoes, black flies, kissing bugs, biting midges, head lice, and ticks. Abstracts of his most developed research endeavors including publications and conferences presentations are described below:

• B Brei, JM Clark, JD Edman. Potential for age-grading Anopheles stephensi (Liston) (Diptera: Culicidae) by gas-chromatographic analysis of cuticular hydrocarbons. (in prep) We quantified time-dependent changes in the cuticular hydrocarbons of female An. stephensi using gas chromatography. The ratio of two prominent hydrocarbons was found to change significantly as the mosquito ages. We then designed an age-grading model for An. stephensi to classify mosquitoes into one of four age categories. Our second model uses known values of sporogony for each of four Plasmodium species to estimate the likelihood that a mosquito could be malaria-infective to humans.
  
  
• B Brei, BW Cribb, and D Merritt. The effects of seawater components on immature Culicoides molestus (Skuse) (Diptera: Ceratopogonidae). Aust J Entomol 42 (2003) (in press). Presented at the Arbovirus Research Association 8th Symposium and the Mosquito Control Association of Australia 4th Symposium. We studied the impact of increasing salinity and seawater concentration on survival of fourth-instar C. molestus larvae. We concluded that artificial elevation of seawater concentration in the sandy substrate potentially reduces immature midge survival.
  
  
• BW Cribb, B Brei, A Ridley, D Merritt. Occurrence of immature Culicoides molestus (Skuse) (Diptera: Ceratopogonidae) in relation to habitat characteristics. Aust J Entomol 42 (2003) (in press). Our analysis of beach sites on the Gold Coast, Australia, found that 14 physical and chemical habitat characteristics differed significantly between those sites where numerous immatures of the canal biting midge, C. molestus were found and where no midge immatures occurred.
  
  
• S Narasimhan, F Santiago, RA Koski, B Brei, JF Anderson, D Fish, E Fikrig. Examination of the Borrelia burgdorferi transcriptome in Ixodes scapularis during feeding. J Bacteriol 184, 3122 (2002). We examined B. burgdorferi gene expression within the guts of engorging I. scapularis ticks by use of differential immunoscreening and differential expression with a customized amplified library. This study demonstrates a new approach to the global analysis of B. burgdorferi genes that are preferentially expressed within the vector during feeding.
  
  
• B Brei, L Beati, and D Fish. Factors specific to tick-feeding enhance Anaplasma phagocytophila transmission and facilitate the establishment of virulent bacterial forms in host blood. Presented at the 4th International Conference on Ticks and Tick-Borne Pathogens and at an ASM Regional Meeting. (in prep) Tick-borne bacterial pathogens require a significant vector feeding time before transmission can occur. Borrelia burgdorferi and Rickettsia rickettsii are infective to vertebrates after they are activated by an interval of tick feeding or elevated temperature. We investigated the activation of Anaplasma phagocytophila, the agent of human granulocytic ehrlichiosis, in Ixodes scapularis ticks to determine if differences in activation could help explain differences in the transmission dynamics of tick-borne bacteria.
  We examined whether A. phagocytophila could be transmitted to C3H mice by inoculation of infected salivary glands from I. scapularis ticks that were incubated at 37°C or fed upon mice for various intervals. At each interval, salivary glands were dissected from the ticks and injected into mice by needle-inoculation. At weekly intervals, blood and ear-tissue samples were collected from both inoculated and parasitized mice. We analyzed the ear-tissue samples by a polymerase chain reaction (PCR) targeting the immunodominant p44 antigen and we analyzed the blood by both a p44 PCR and an indirect immunofluorescence assay (IFA). The viability of inoculated A. phagocytophila preparations was confirmed with a fluorescence-based assay for bacterial cell viability. The number of A. phagocytophila in inocula was quantified using a competitive PCR targeting a variable region of the 16S rRNA gene sequence. Results indicated that mice became infected only after feeding ticks for =24h or being inoculated with salivary glands from ticks that fed for 48h. Needle-inoculation of infected salivary glands from ticks that were incubated for various intervals did not produce infection. All mice that were inoculated in this study received >106 viable A. phagocytophila, a dose >100 times the median infectious dose for C3H mice inoculated with infected mouse blood. This study shows that factors specific to tick feeding enhance A. phagocytophila transmission and facilitate the establishment of virulent bacterial forms in host blood. The establishment of these factors is dependent on tick feeding time, affording a brief "grace period" prior to infection with this pathogen.
  
  
• B Brei, JE George, JM Pound, JA Miller, TJ Daniels, RC Falco, KC Stafford III, TL Schulze, TN Mather, JF Carroll, D Fish. Evaluation of the USDA Northeast Area-wide Tick Control Project by meta-analysis. Presented at the IX International Conference on Lyme Borreliosis and the 2001 Annual Meeting of the ESA. (in prep) An initiative was started in 1997 to demonstrate that a tick control strategy focused on white-tailed deer, the major hosts for adult Ixodes scapularis ticks, could reduce human risk for Lyme disease and other tick-borne diseases in endemic communities of the Northeastern USA. White-tailed deer were treated with Point-Guard (2% amitraz) using the USDA-ARS patented '4-poster' device. Questing nymphal I. scapularis ticks were sampled in control and treatment sites in Rhode Island, Connecticut, New York, New Jersey, and Maryland in five concurrent studies to assess the efficacy of treatment. A meta-analysis was constructed with tick collection data from 1998-2002 to derive an overall assessment of the project's success to date. The meta-analysis accounts for differences in sample size, effect variance, sampling method, and season. The meta-analysis shows an increasing trend of efficacy for the control strategy within treatment sites of 1.28 km radius, demonstrating that a high level of tick control can be achieved by treating white-tailed deer.
  
  
• B Brei and D Fish. Comment on Sex-biased Parasitism and Mortality of Mammals. Science 55 (2003). Sexual difference in mammalian home range is a proximate mechanistic basis for sex-biased parasitism that Moore and Wilson did not consider (Science, Research Articles, 20 Sep. 2002, p. 2015). Neither this study nor Owens' analysis of human mortality data support male immuno-inferiority, as Owens suggests (Perspectives, 20 Sep. 2002, p. 2008).
  

The Zoonotic Maintenance of Borrelia spirochetes in the Northeastern United States

Brandon's dissertation research focused on the ecology of vector-borne spirochetes, including the Lyme disease pathogen, Borrelia burgdorferi, and a recently discovered relapsing fever group (RFG) Borrelia. The primary aim was to determine how these tick-borne Borrelia populations are maintained in nature. His studies were thus designed to answer the following questions: (1) Do Borrelia populations differ in composition between vertebrate host species? (2) Which vertebrate species have the greatest impact on the infection prevalence of ticks with Borrelia genotypes pathogenic to humans? (3) What is the genetic mechanism by which Borrelia spirochetes infect a diverse array of vertebrate hosts?

In the summer of 2002, he began trapping small and medium-sized mammals using live traps arranged in trapping webs. He collected blood and tissue samples from mice, raccoons, squirrels, chipmunks, opossums, and shrews, thereby amassing Borrelia samples from a diverse array of vertebrate hosts. Additionally, animals were caged over pans of water for three days to recover engorged ticks that detached after feeding. These ticks were then allowed to molt in an incubator to assess the diversity of Borrelia acquired from various host species. He also regularly drag-sampled questing ticks to estimate the seasonal abundance of ticks in the environment, as well as to acquire Borrelia from ticks that have maintained spirochetes over winter. Brandon was processing these samples in the laboratory.

His thesis research was designed to contribute to a better understanding of the zoonotic maintenance of vector-borne Borrelia populations in nature. Determining if the genetic compositions of Borrelia populations differ between vertebrate host species would indicate whether Borrelia strains differ in infectivity and potentially pathogenicity. Determining the important reservoirs of human pathogens would facilitate better-defined Lyme disease risk factors and more effectively designed control methods. Finally, if a genetic mechanism for the zoonotic maintenance of Borrelia could be elucidated, this would have wide-ranging implications for the study of vector-borne zoonoses and might indicate how some human pathogenic infections emerge.

To gain knowledge in the diverse disciplines of his professional interest, Brandon was involved in three reading groups: Ecology of Wildlife Disease, Vector Biology, and Population Genetics of Vectors. Brandon also attended academic conferences on tropical medicine (ASTMH), entomology (ESA), microbiology (ASM), Australian arbovirology, West Nile virus, Lyme Borreliosis, and ticks and tick-borne pathogens. His graduate coursework was selected with the interdisciplinary nature of vector biology in mind, with courses such as molecular genetics of bacteria, landscape ecology, and evolutionary theory.

To develop skills as an instructor, Brandon taught weekly entomology classes in a community-based program and was a teaching assistant for the graduate Vector Biology course at Yale. Through two field-based projects, he has supervised the research efforts of an undergraduate and two M.P.H. students, and was a mentor for an undergraduate's laboratory-based project.