A British Society for Haematology Guideline: Diagnosis and management of thrombotic thrombocytopenic purpura and thrombotic microangiopathies.

The objective of this guideline is to provide healthcare professionals with clear, up-to-date and practical guidance on the management of thrombotic thrombocytopenic purpura (TTP) and related thrombotic microangiopathies (TMAs), including complement-mediated haemolytic uraemic syndrome (CM HUS); these are defined by thrombocytopenia, microangiopathic haemolytic anaemia (MAHA) and small vessel thrombosis. Within England, all TTP cases should be managed within designated regional centres as per NHSE commissioning for highly specialised services.

A British Society for haematology guideline: diagnosis and management of thrombotic thrombocytopenic purpura and thrombotic microangiopathies

The objective of this guideline is to provide healthcare professionals with clear, up-to-date and practical guidance on the management of thrombotic thrombocytopenic purpura (TTP) and related thrombotic microangiopathies (TMAs), including complement-mediated haemolytic uraemic syndrome (CM HUS); these are defined by thrombocytopenia, microangiopathic haemolytic anaemia (MAHA) and small vessel thrombosis. Within England, all TTP cases should be managed within designated regional centres as per NHSE commissioning for highly specialised services.

Surgery in patients with inherited bleeding disorders.

It is estimated that up to 1% of the general population has a congenital bleeding disorder. With this level of disease burden, it is more likely than not that any practising surgeon or anaesthetist will, at one time or another, have occasion to manage one such patient. Congenital haemophilia, both A and B, von Willebrand's disease, and inherited qualitative platelet defects, constitute the bulk of these disorders, with the rest distributed between much rarer conditions. Although looking after such patients will continue to pose a challenge to anaesthetists, recent and continuing advances in haemostatic products, coupled with increasing awareness of haemostatic care, means that surgery in this challenging group of patients is safer now than ever before, and can now be undertaken with a degree of confidence not possible even two decades ago. Central to these recent successes has been the continuing evolution of specialised healthcare services; in particular, Haemophilia Comprehensive Care Centres. Of equal importance, at least in developed countries, has been the ease of access to highly purified, safe and effective haemostatic products. The key to successful surgical management of the patient with a bleeding disorder is a multidisciplinary approach involving not only surgeons, anaesthetists and haematologists, but also laboratory scientists, specialist physiotherapists and haemophilia nurses. With careful planning, most surgical and invasive procedures can be carried out safely in persons with haemophilia and other bleeding disorders.

Modeling and mitigating winter hay bale damage by elk in a low prevalence bovine tuberculosis endemic zone.

Wildlife causes extensive crop damage throughout much of North America and these shared feeds are a key risk factor in the transmission of diseases between wildlife and livestock, including bovine tuberculosis (TB). Predicting wildlife use of agricultural crops can provide insight directed toward targeted disease mitigation at areas of potential indirect interaction. In this study, we quantified use of hay bales by elk (Cervus canadensis) during the winter in southwestern Manitoba, Canada using a database of 952 damage claims paid compensation from 1994 to 2012. We evaluated environmental factors predicted to determine risk of hay bale damage on each quarter section by elk using a Resource Selection Probability Function (RSPF) model. The most important variables (as measured for each quarter section and based on cumulative Akaike weights that scale from 0 to 1) were distance to protected areas (1.00), forest including a buffer around the quarter section (1.00), forage crop including a buffer around the quarter section (1.00), distance from streams (0.99), forage crop (0.92), cereal and oilseed crop cover including a buffer (0.85), and forest cover (0.82). We then developed an RSPF-based predictive map of damage to hay bales by elk that identified key areas with high probability of damage (RSPF≥0.6), accounting for 3.5% of the study area. We then multiplied the RSPF values by the inverse of the proximity to known cases of TB positive elk and determined that 0.51% of the study area had an overall high combined probability of hay bale damage and proximity to TB positive elk (i.e. adjusted probability of ≥0.6). In the southern half of the study area where 164 hay yard barrier fences have been implemented since 2002, there has been a significant decrease in the number of annual claims. Barrier fencing around Riding Mountain National Park has been successful at reducing elk damage where it has been implemented. In our study area, prevalence of TB in both cattle (0.003%) and elk (0.89%) is very low, precluding conventional epidemiological analyses. In the absence of clear evidence of specific routes of TB transmission, we advocate that on-farm risk assessments and mitigation efforts should continue to address areas where elk cause damage to hay bales in winter using barrier fencing. Mitigation effort should especially focus on areas where TB positive elk have been identified, as these sites provide potential for indirect interaction between cattle and elk.

Mutations in MYH7 cause Multi-minicore Disease (MmD) with variable cardiac involvement.

Central Core Disease (CCD) and Multi-minicore Disease (MmD) (the "core myopathies") have been mainly associated with mutations in the skeletal muscle ryanodine receptor (RYR1) and the selenoprotein N (SEPN1) gene. A proportion of cases remain unresolved. Mutations in MYH7 encoding the beta myosin heavy chain protein have been implicated in cardiac and, less frequently, skeletal muscle disorders. Here we report four patients from two families with a histopathological diagnosis of MmD, presenting in childhood with slowly progressive muscle weakness, more proximal in Family 1 and more distal in Family 2, and variable degrees of cardiorespiratory impairment evolving later in life. There was also a strong family history of sudden death in the first family. Muscle biopsies obtained in early childhood showed multiple minicores as the most prominent feature. Sequencing of the MYH7 gene revealed heterozygous missense mutations, c.4399C>G; p.Leu1467Val (exon 32) in Family 1 and c.4763G>C; p.Arg1588Pro (exon 34) in Family 2. These findings suggest MYH7 mutations as another cause of a myopathy with multiple cores, in particular if associated with dominant inheritance and cardiac involvement. However, clinical features previously associated with this genetic background, namely a more distal distribution of weakness and an associated cardiomyopathy, may only evolve over time.

Analyzing the success of T-matrix diagrammatic theories in representing a modified Hubbard model.

We present a systematic study of various forms of renormalization that can be applied in the calculation of the self-energy of the Hubbard model within the T-matrix approximation. We compare the exact solutions of the attractive and repulsive Hubbard models, for linear chains of lengths up to eight sites, with all possible taxonomies of the T-matrix approximation. For the attractive Hubbard model, the success of a minimally self-consistent theory found earlier in the atomic limit (Verga et al 2005 Phys. Rev. B 71 155111) is not maintained for finite clusters unless one is in the very strong correlation limit. For the repulsive model, in the weak correlation limit at low electronic densities-that is, where one would expect a self-consistent T-matrix theory to be adequate-we find the fully renormalized theory to be most successful. In our studies we employ a modified Hubbard interaction that eliminates all Hartree diagrams, an idea which was proposed earlier (Zlatic et al 2000 Phys. Rev. B 63 035104).

Congenital toxoplasmosis in two health institutions in Trinidad.

Toxoplasmosis is the most widespread zoonosis and an important human disease particularly in children where it could cause visual and neurological impairment and mental retardation. This study was conducted to determine the prevalence of toxoplasmosis, especially congenital toxoplasmosis in patients at two health institutions in Trinidad A total of 504 cord blood samples of newborn babies were collected: 174 from a women's hospital and 330 from a general hospital. In order to elicit aternal and prenatal risk factors for toxoplasmosis, mothers of the newborns completed a questionnaire. Enzyme-immuno assay (EIA) was used to detect IgG and IgM to Toxoplasma gondii. Overall, of 504 serum samples tested, 220 (43.7%) were seropositive for IgG while the prevalence of congenital toxoplasmosis as reflected by IgM was 0.4%. The prevalence of IgG and IgM by health institutions was not significantly different (p > 0.05; chi-square). The prevalence of toxoplasmosis using IgG was highest in neonates of mothers who were of East Indian descent (54.1%), had four children (52.9%), kept cats in households (47.7%), practised outdoor gardening (50.8%), consumed raw meat (66.7%), had experienced miscarriage(s) (47.3%), stillbirths (66.7%), or who had eye problem(s) (52.9%) and mental retardation (50.0%). The study prevalence of congenital toxoplasmosis revealed a high seroprevalence oftoxoplasmosis in neonates but there was 0.4% serological evidence of congenital disease. It indicates a need for sensitization of the population and healthcare workers and for follow-up of infected children for clinical evidence of the disease. This would be necessary to fully appreciate the impact of toxoplasmosis in Trinidad and Tobago. The differences from comparison groups were however not statistically significant (p > 0.05; chi-square).

Congenital cataract, ataxia, external ophthalmoplegia and dysphagia in two siblings. A Marinesco-Sjögren-like syndrome.

Marinesco-Sjögren syndrome (MSS) is an autosomal recessive multiorgan disorder with clinical and genetic heterogeneity. The key features of MSS include cerebellar ataxia, early bilateral cataracts, delayed motor development, and to a varying degree mental retardation. The syndrome was recently mapped to chromosome 5q31, and loss-of-function mutations in the SIL1 gene have been identified as the primary pathology. Here, we describe two German siblings with clinical characteristics resembling those seen in many cases of MSS except that a marked cerebellar atrophy was not detectable in our patients. In addition, both patients presented with external ophthalmoplegia and paralytic dysphagia. Sequencing of all 10 exons of the SIL1 gene did not detect any SIL1 mutation in our patients.

Congenital toxoplasmosis in two health institutions in Trinidad / Toxoplasmosis congénita en dos centros de salud de Trinidad

Toxoplasmosis is the most widespread zoonosis and an important human disease particularly in children where it could cause visual and neurological impairment and mental retardation. This study was conducted to determine the prevalence of toxoplasmosis, especially congenital toxoplasmosis in patients at two health institutions in Trinidad A total of 504 cord blood samples of newborn babies were collected: 174 from a women's hospital and 330 from a general hospital. In order to elicit aternal and prenatal risk factors for toxoplasmosis, mothers of the newborns completed a questionnaire. Enzyme-immuno assay (EIA) was used to detect IgG and IgM to Toxoplasma gondii. Overall, of 504 serum samples tested, 220 (43.7%) were seropositive for IgG while the prevalence of congenital toxoplasmosis as reflected by IgM was 0.4%. The prevalence of IgG and IgM by health institutions was not significantly different (p > 0.05; chi-square). The prevalence of toxoplasmosis using IgG was highest in neonates of mothers who were of East Indian descent (54.1%), had four children (52.9%), kept cats in households (47.7%), practised outdoor gardening (50.8%), consumed raw meat (66.7%), had experienced miscarriage(s) (47.3%), stillbirths (66.7%), or who had eye problem(s) (52.9%) and mental retardation (50.0%). The study prevalence of congenital toxoplasmosis revealed a high seroprevalence oftoxoplasmosis in neonates but there was 0.4% serological evidence of congenital disease. It indicates a need for sensitization of the population and healthcare workers and for follow-up of infected children for clinical evidence of the disease. This would be necessary to fully appreciate the impact of toxoplasmosis in Trinidad and Tobago. The differences from comparison groups were however not statistically significant (p > 0.05; chi-square).

La toxoplasmosis es la zoonosis más extendida y una enfermedad humana importante, particularmente en niños, a quienes puede causar daño visual y neurológico, y retraso mental. Este estudio se llevó a cabo con el propósito de determinar la prevalencia de la toxoplasmosis, especialmente la toxoplasmosis congénita en pacientes de dos centros de salud en Trinidad. Se recogieron un total de 504 muestras de sangre de cordón umbilical de neonatos: 174 de mujeres en un hospital de mujeres y 330 en un hospital general. A fin de obtener información sobre los factores de riesgo maternos y prenatales en relación con la toxoplasmosis, las madres de los recién nacidos llenaron una encuesta. Un ensayo inmunoenzimático (EIE) fue usado para detectar anticuerpos IgG e IgM contra el Toxoplasma gondii. En general, de 504 muestras de suero examinadas, 220 (43.7%) resultaron seropositivas al IgG, mientras que la prevalencia de la toxoplasmosis congénita reflejada por el IgM fue 0.4%. La prevalencia de IgG e IgM por parte de las instituciones de salud no fue significativamente diferente (p > 0.05; chi-cuadrado). La prevalencia de la toxoplasmosis usando IgG fue más alta en los neonatos cuyas madres eran ascendencia indoriental (54.1%), tenían cuatro niños (52.9%), mantenían gatos en sus casas (47.7%), practicaban jardinería al aire libre (50.8%), consumían carne cruda (66.7%), habían tenido aborto(s) (47.3%), partos de feto muerto (66.7%), o tenían problema(s) de los ojos (52.9%) y retardo mental (50.0%). Este estudio de la toxoplasmosis congénita, reveló una alta seroprevalencia de toxoplasmosis en neonatos, pero hubo 0.4% de evidencia serológica de enfermedad congénita. Esto apunta a la necesidad de sensibilizar a la población y a los trabajadores del cuidado de la salud, e igualmente indica la necesidad de realizar seguimientos a los niños infectados, en busca de evidencia clínica de la enfermedad. Esto es necesario si se quiera valorar totalmente el impacto de la...

The tsetse fly Glossina palpalis palpalis is composed of several genetically differentiated small populations in the sleeping sickness focus of Bonon, Côte d'Ivoire.

Glossina palpalis is the main vector of human African trypanosomosis (HAT, or sleeping sickness) that dramatically affects human health in sub-Saharan Africa. Because of the implications of genetic structuring of vector populations for the design and efficacy of control campaigns, G. palpalis palpalis in the most active focus of sleeping sickness in Côte d'Ivoire was studied to determine whether this taxon is genetically structured. High and statistically significant levels of within population heterozygote deficiencies were found at each of the five microsatellite loci in two temporally separated samples. Neither null alleles, short allele dominance, nor trap locations could fully explain these deviations from random mating, but a clustering within each of the two samples into different genetic sub-populations (Wahlund effect) was strongly suggested. These different genetic groups, which could display differences in infection rates and trypanosome identity, were composed of small numbers of individuals that were captured together, leading to the observed Wahlund effect. Implications of this population structure on tsetse control are discussed.

Role of strong electronic correlations in the metal-to-insulator transition in disordered LiAlyTi2-yO4.

The compound LiAlyTi2-yO4 undergoes a metal-to-insulator transition for yc approximately 0.33. It is known that disorder alone is insufficient to explain this transition; e.g., a quantum site percolation model predicts yc approximately 0.8. We have included (Hubbard) electronic interactions into a model of this compound, using a real-space Hartree-Fock approach that achieves self-consistency at every site, and have found that for a Hubbard energy equal to 1.5 times the non-interacting bandwidth one obtains yc approximately 0.3. Further, with increasing Hubbard energy we find an Altshuler-Aronov suppression of the density of states, deltaN(epsilon) approximately square root /epsilon-epsilonF/, that reduces the density of states at the Fermi energy to zero at the critical Hubbard interaction. Using this ratio of correlation to hopping energy one is led to a prediction of the near-neighbor superexchange (J/t approximately 1/3) which is similar to that for the cuprate superconductors.

A novel Gypsy founder mutation, p.Arg1109X in the CMT4C gene, causes variable peripheral neuropathy phenotypes.

BACKGROUND: Linkage, haplotype and sequencing analysis in a large Spanish Gypsy kindred with multiple members affected by autosomal recessive peripheral neuropathy led to the identification of a novel mutation, p.Arg1109X, in the CMT4C gene. The screening of further unrelated patients, and of a panel of ethnically matched controls, showed that p.Arg1109X is an ancestral mutation which occurs in Gypsy populations across Europe and is the most common cause of autosomal recessive Charcot-Marie-Tooth disease in Spanish Gypsies. OBJECTIVE: To report the identification of a novel Gypsy founder mutation causing autosomal recessive CMT4C disease in a sample of homozygous affected individuals. RESULTS: The mutation was associated with a surprisingly broad spectrum of neuropathy phenotypes, with variation in the age at onset, rate of progression, severity of muscle and sensory involvement, the presence of scoliosis, and cranial nerve involvement. CONCLUSIONS: Ascertainment and further studies of CMT4C patients in this population will provide a unique opportunity for characterising the full range of clinical manifestations of the disease in a genetically homogeneous sample.

Identification of midgut proteins that are differentially expressed in trypanosome-susceptible and normal tsetse flies (Glossina morsitans morsitans).

Molecules in the midgut of tsetse flies (Diptera: Glossinidiae) are thought to play important roles in the life cycle of African trypanosomes by influencing initial parasite establishment and subsequent differentiation events that ultimately lead to maturation of mammal-infective trypanosomes. The molecular composition of the tsetse midgut is, therefore, of critical importance to disease transmission by these medically important vectors. In this study we compared protein expression profiles of midguts of the salmon mutant and wild type Glossina morsitans morsitans Westwood that display marked differences in their susceptibility to infection by African trypanosomes. Isotope coded affinity tag (ICAT) technology was used to identify 207 proteins including 17 that were up regulated and nine that were down regulated in the salmon mutants. Several of the up regulated molecules were previously described as tsetse midgut or salivary gland proteins. Of particular interest was the up regulation in the salmon flies of tsetse midgut EP protein, a recently described molecule with lectin-like activity that was also found to be induced in tsetse by bacterial challenge. The up regulation of the EP protein in midguts of salmon mutants was confirmed by two-dimensional gel electrophoresis and tandem mass spectrometry.

Tsetse genetics: contributions to biology, systematics, and control of tsetse flies.

Tsetse flies (Diptera: Glossinidae) constitute a small, ancient taxon of exclusively hematophagous insects that reproduce slowly and viviparously. Because tsetse flies are the only vectors of pathogenic African trypanosomes, they are a potent and constant threat to humans and livestock over much of sub-Saharan Africa. Despite their low fecundity, tsetse flies demonstrate great resilience, which makes population suppression expensive, transient, and beyond the capacities of private and public sectors to accomplish, except over small areas. Nevertheless, control measures that include genetic methods are under consideration at national and supranational levels. There is a pressing need for sufficient laboratory cultures of tsetse flies and financial support to carry out genetic research. Here we review tsetse genetics from organismal and population points of view and identify some research needs.

Monitoring the susceptibility of Glossina palpalis gambiensis and G. morsitans morsitans to experimental infection with savannah-type Trypanosoma congolense, using the polymerase chain reaction.

Teneral Glossina palpalis gambiensis and G. morsitans morsitans (Diptera: Glossinidae) were fed on mice infected with savannah-type Trypanosoma (Nannomonas) congolense. The infection was monitored by checking the post-feeding diuresis fluid (midgut infection) and saliva (mature infection) of individual flies for parasites, at different times post-infection, using microscopical examination and a PCR-based assay. The results indicated that both tsetse species supported established midgut infections by 10 days post-infection and that maturation occurred after 24 days in G. m. morsitans. Although, for both diuresis fluid and saliva, the results of the microscopy showed good concordance with those of the PCR, the PCR identified more positive samples. Monitoring allowed determination of the status of the infection in individual flies, which was confirmed, 48 days post-infection, by the microscopical examination of the midguts and probosces dissected out of the flies and by the PCR-based amplification of any trypanosome DNA in these organs. Again, in terms of the detection of trypanosomes in the dissected organs, there was good concordance between the results of the PCR and those of the microscopy, although PCR revealed many more mature infections than did microscopical examination, particularly in the G. p. gambiensis investigated. There was a higher prevalence of immature infection in G. p. gambiensis than in G. m. morsitans (P<0.05) but the inter-specific differences seen in the prevalences of any infection and of mature infection were not statistically significant. The intrinsic vectorial capacity for T. congolense of both tsetse species therefore appeared quite similar, although the true vectorial competence of G. p. gambiensis remains to be determined.

Photographic polytene chromosome maps for Glossina morsitans submorsitans (Diptera: Glossinidae): cytogenetic analysis of a colony with sex-ratio distortion.

Photographic polytene chromosome maps from trichogen cells of pharate adult Glossina morsitans submorsitans were constructed. Using the standard system employed to map polytene chromosomes of Drosophila, the characteristic landmarks were described for the X chromosome and the two autosomes (L1 and L2). Sex-ratio distortion, which is expressed in male G. m. submorsitans, was found to be associated with an X chromosome (X8) that contains three inversions in each arm. Preliminary data indicate no differences in the fecundity of X(A)X(A) and X(A)X(B) females, but there are indications that G. m. submorsitans in colonies originating from Burkina Faso and Nigeria have genes on the autosomes and (or) the Y chromosome that suppress expression of sex-ratio distortion.

Identification of major soluble salivary gland proteins in teneral Glossina morsitans morsitans.

Salivary glands of tsetse flies (Diptera: Glossinidiae) contain molecules that are involved in preventing blood clotting during feeding as well as molecules thought to be intimately associated with trypanosome development and maturation. Here we present a protein microchemical analysis of the major soluble proteins of the salivary glands of Glossina morsitans morsitans, an important vector of African trypanosomes. Differential solubilization of salivary proteins was followed by reverse-phase, high-performance liquid chromatography (HPLC) and analysis of fractions by 1-D gel electrophoresis to reveal four major proteins. Each protein was subjected to amino acid microanalysis and N-terminal microsequencing. A protein chemical approach using high-resolution 2-D gel electrophoresis and mass spectrometry was also used to identify the salivary proteins. Matrix-assisted, laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry and quadrupole time-of-flight (Q-TOF) tandem mass spectrometry methods were used for peptide mass mapping and sequencing, respectively. Sequence information and peptide mass maps queried against the NCBI non-redundant database confirmed the identity of the first protein as tsetse salivary gland growth factor-1 (TSGF-1). Two proteins with no known function were identified as tsetse salivary gland protein 1 (Tsal 1) and tsetse salivary gland protein 2 (Tsal 2). The fourth protein was identified as Tsetse antigen-5 (TAg-5), which is a member of a large family of anti-haemostatic proteins. The results show that these four proteins are the most abundant soluble gene products present in salivary glands of teneral G. m. morsitans. We discuss the possible functions of these major proteins in cyclical transmission of African trypanosomes.

Genetic identity of Marinesco-Sjögren/myoglobinuria and CCFDN syndromes.

OBJECTIVE AND BACKGROUND: To describe three Gypsy families with Marinesco-Sjögren syndrome (MSS), demyelinating neuropathy, and recurrent episodes of myoglobinuria in five of the six affected subjects. Because these families originated from the same genetically isolated founder population as did patients with congenital cataracts facial dysmorphism neuropathy (CCFDN) syndrome, and because the two syndromes have clinical manifestations in common, we hypothesized that the two related, albeit distinct, syndromes may represent clinical variants of a single genetic disorder. METHODS: Clinical studies were conducted and linkage and haplotype analyses were performed for the three families. A total of 16 individuals, including the 6 with MSS and 10 unaffected relatives, were genotyped for six polymorphic microsatellite markers from the CCFDN region on 18qter. RESULTS: Linkage analysis of markers in the 18qter region, where we previously had located the CCFDN gene, produced a lod score of 3.55, demonstrating colocalization of the gene responsible for MSS with demyelinating neuropathy and myoglobinuria with the CCFDN gene. Moreover, the patients with MSS shared the conserved marker haplotype found in CCFDN chromosomes. CONCLUSIONS: These data suggest that Marinesco-Sjögren syndrome with peripheral neuropathy and myoglobinuria, and congenital cataracts facial dysmorphism neuropathy syndrome are genetically identical and are caused by a single founder mutation.

The major protein in the midgut of teneral Glossina morsitans morsitans is a molecular chaperone from the endosymbiotic bacterium Wigglesworthia glossinidia.

Molecules in the midgut of the tsetse fly (Diptera: Glossinidiae) are thought to play an important role in the life cycle of African trypanosomes by influencing their initial establishment in the midgut and subsequent differentiation events that ultimately affect parasite transmission. It is thus important to determine the molecular composition of the tsetse midgut to aid in understanding disease transmission by these medically important insect vectors. Here, we report that the most abundant protein in the midguts of teneral (unfed) Glossina morsitans morsitans is a 60 kDa molecular chaperone of bacterial origin. Two species of symbiotic bacteria reside in the tsetse midgut, Sodalis glossinidius and Wigglesworthia glossinidia. To determine the exact origin of the 60 kDa molecule, a protein microchemical approach involving two-dimensional (2-D) gel electrophoresis and mass spectrometry was used. Peptide mass maps were compared to virtual peptide maps predicted for S. glossinidius and W. glossinidia 60 kDa chaperone sequences. Four signature peptides were identified, revealing that the source of the chaperone was W. glossinidia. Comparative 2-D gel electrophoresis and immunoblotting further revealed that this protein was localized to the bacteriome and not the distal portion of the tsetse midgut. The possible function of this highly abundant endosymbiont chaperone in the tsetse midgut is discussed.

Hybridization asymmetries in tsetse (Diptera: Glossinidae): role of maternally inherited factors and the tsetse genome.

Among the morsitans-group of tsetse there are several pairs of taxa in which there is a marked hybridization asymmetry (HA), i.e., one cross produces significantly more offspring than does the reciprocal cross. To investigate the relative contribution of maternally inherited factors (MIF) and chromosomal factors to HA, three hybrid lines were established in which flies have MIF from one taxon and chromosome from another. HA was then compared among crosses of the parental taxa and crosses of each parental taxon with the appropriate hybrid line. The results indicate that HA in reciprocal crosses of Glossina morsitans morsitans Westwood and Glossina swynnertoni Austin and in reciprocal crosses of G. m. morsitans and Glossina morsitans centralis Machado are caused by chromosomal factors, not MIF. Reciprocal crosses of G. m. centralis and G. swynnertoni do not display HA, and none developed as a result of a novel combination of MIF and tsetse chromosomes.