Journal of the American Association for Laboratory Animal Science, 2019
Many variables can influence animal behavior and physiology, potentially affecting scientific stu... more Many variables can influence animal behavior and physiology, potentially affecting scientific study outcomes. Laboratory and husbandry procedures—including handling, cage cleaning, injections, blood collection, and animal identification—may produce a multitude of effects. Previous studies have examined the effects of such procedures by making behavioral and physiologic measurements at specific time points; this approach can be disruptive and limits the frequency or duration of observations. Because these procedures can have both acute and long-term effects, the behavior and physiology of animals should be monitored continuously. We performed a retrospective data analysis on the effects of 2 routine procedures, animal identification and cage changing, on motion and breathing rates of mice continuously monitored in the home cage. Animal identification, specifically tail tattooing and ear tagging, as well as cage changing, produced distinct and reproducible postprocedural changes in sp...
Journal of the American Mosquito Control Association, 1990
The potential for Anopheles egg survival in dry soil from larval development sites was investigat... more The potential for Anopheles egg survival in dry soil from larval development sites was investigated in western Kenya. A total of 230 dry soil samples collected in 1987, 1988 and 1989 yielded 126 first-instar Anopheles gambiae s.l. larvae from 2 to 5 days after flooding with water. These larvae were from dried animal hoofprints along streams (57.9%), from dried edges of permanent and temporary pools (41.3%) and from dried stream beds (0.8%). Larval density was 1.2 larvae/kg of soil from positive microhabitats in 1987 and 2.4 larvae/kg in 1988. Thirteen larvae from the 1989 soil samples, reared to adults, were identified by DNA probes as Anopheles gambiae sensu strictu (n = 6) and Anopheles arabiensis (n = 7). Experimentally, eggs from field-collected females remained viable up to 12 days for An. gambiae s.l. and 10 days for An. funestus. In western Kenya, egg viability in dry soil may represent a significant, short-term survival mechanism for 2 species of the An. gambiae complex.
Journal of the American Mosquito Control Association
At 2 sites in western Kenya targeted for future malaria vaccine trials, adult culicine mosquitoes... more At 2 sites in western Kenya targeted for future malaria vaccine trials, adult culicine mosquitoes were sampled over one year by 5 collection techniques to assess human exposure to potential vectors of pathogens other than malaria. Collections included 20,910 females representing 19 species in Kisian and 4,312 females of 11 species in Saradidi. Common species in Kisian included Culex quinquefasciatus (71.4%), Mansonia uniformis (15.8%), Ma. africana (6.2%), Aedes mcintoshi (2.0%), Coquillettidia fuscopennata (1.9%) and Ae. ochraceus (1.8%). Common species in Saradidi included Cx. quinquefasciatus (92.7%), Cx. nebulosus (4.5%) and Ma. uniformis (1.0%). Human-bait collections identified 16 man-biting culicine species in Kisian and 9 in Saradidi. Man-biting rates at Kisian for the 5 most common species were 1.8, 14.6 and 13.5 times higher than at Saradidi for indoor, outdoor and tent collections, respectively. Exposure indoors was estimated to be 1,277 bites/man/year at Kisian and 720 a...
Journal of the American Mosquito Control Association
Floodwater Aedes breeding habitats in central Kenya were sequentially flooded to determine the nu... more Floodwater Aedes breeding habitats in central Kenya were sequentially flooded to determine the numbers of mosquito eggs hatching during each flooding. Approximately 90% of the larvae sampled during 4 floodings emerged during the initial flooding. The number of Aedes eggs hatching during the second flooding was lowest of all 4 floodings, and no significant differences in the amount of egg hatching during floodings 3 and 4 were seen. Unhatched Aedes eggs were present in soil samples collected after the final flooding. The possible implications of these findings with regard to Rift Valley fever virus control are discussed.
In rodent malaria model systems, protective immunity induced by immunization with irradiated spor... more In rodent malaria model systems, protective immunity induced by immunization with irradiated sporozoites is eliminated by in vivo depletion of CD8+ T cells, and adoptive transfer of CTL clones against the circumsporozoite protein protects against malaria. We recently demonstrated that volunteers immunized with irradiated Plasmodium falciparum sporozoites produce CTL against peptide 368-390 of the P. falciparum circumsporozoite protein. To determine whether natural exposure to malaria induced similar CTL, we studied 11 adult, male, life-long residents of a highly malarious area of Kenya, who were selected because their lymphocytes had been shown to proliferate after stimulation with peptides 361-380, 371-390, or 368-390 and because nine had been resistant to malaria in previous studies. In four of the 11 individuals there was peptide-specific, genetically restricted, CTL activity. In all four individuals, this activity was unaffected by depletion of CD4+ T cells. In three volunteers ...
Journal of the American Mosquito Control Association, 1990
Effectiveness of sustained-release Altosid pellets (4% AI methoprene) against floodwater mosquito... more Effectiveness of sustained-release Altosid pellets (4% AI methoprene) against floodwater mosquitoes in dambos treated at 5, 3, and 1 wk before and 1 day after flooding was determined. Only 2% of Aedes pupae (primarily Aedes mcintoshi) survived to adults in an area treated 5 wk preflood, and no adult mosquitoes emerged from an area treated 1 day after flooding. In contrast, 12 and 16% of Aedes pupae successfully survived to the adult stage in areas pretreated 3 and 1 wk, respectively, preflood. The effectiveness of the Altosid declined against Culex spp. (primarily Cx. antennatus) collected from dambos 15-31 days after flooding. The potential for using preflood treatment with methoprene to control Aedes vectors of Rift Valley fever virus in endemic areas is discussed.
The American journal of tropical medicine and hygiene, 1999
A two-year study was conducted of phlebotomine sand fly fauna in a defined focus of Leishmania tr... more A two-year study was conducted of phlebotomine sand fly fauna in a defined focus of Leishmania tropica. A total of 17,947 sand flies representing 10 species were collected from the location. Phlebotomus guggisbergi, a vector of L. tropica in Kenya, was the most prevalent species through the entire period, representing about 80% of the total catch. There was marked seasonal fluctuation in the populations of the three most common species, with highest population levels reached in December and lowest levels reached in July and August. Leishmania-like infections were encountered in 489 P. guggisbergi. No flagellate infections were observed in any other species of sand fly. Although infected P. guggisbergi were collected during each month of the year, the percent parous infected flies was highest (27.5%) during the November through January time period. These data show that the greatest risk of transmission to humans at this focus occurs during December, when the vector is prevalent and i...
The American journal of tropical medicine and hygiene, 1993
In the early 1930s, investigators of visceral leishmaniasis stated that Leishman-Donovan bodies a... more In the early 1930s, investigators of visceral leishmaniasis stated that Leishman-Donovan bodies are found in body fluids of kala-azar patients, for example, in urine, feces, semen, and nasal and pharyngeal secretions. Based on this finding, we investigated the diagnostic potential of nasal secretions, tonsillopharyngeal mucosal swabs, and urine centrifugates inoculated into Schneider's Drosophila Medium (containing antibiotics and antifungal agents) as well as with Giemsa-stained smears. Consequently, 64 randomly selected patients with visceral leishmaniasis from Kenya (59 who were splenic culture or Giemsa stain positive and five who were culture negative but Giemsa stain positive) were tested by three noninvasive methods. These tests were all performed before the patients were treated with Pentostam. Cultures of nasal and tonsillopharyngeal swabs and urine centrifugates produced 28 positive samples representing 24 patients (37.5%). Moreover, a set of 25 Giemsa-stained slide sm...
Journal of the American Mosquito Control Association, 1993
The effect of controlled burning on the survival of Aedes mosquito eggs was evaluated in 2 distin... more The effect of controlled burning on the survival of Aedes mosquito eggs was evaluated in 2 distinct dambo habitats. In a dambo dominated by grasses, egg survival was 3.3% after burning compared with 43.8% in a similar dambo that was not burned. In a dambo dominated by sedges, egg survival was 0.7% after burning compared with 28.5% in a similar dambo that was not burned. Mortality of mosquito eggs appeared to be caused by high temperatures associated with the fire and not elapsed time since egg survival did not decrease with time after burning. The potential for burning to control the mosquito vectors of Rift Valley fever virus is discussed.
The American journal of tropical medicine and hygiene, 1993
The elimination of serum from Plasmodium falciparum culture media could decrease costs, enhance p... more The elimination of serum from Plasmodium falciparum culture media could decrease costs, enhance procurement, and improve the feasibility of large-scale production of parasite material. We provide a semi-defined, serum-free formulation, of commercially available constituents that supports P. falciparum parasite growth at rates comparable with those obtained with serum-supplemented media. The medium is composed of RPMI 1640 to which HEPES, extra glucose, bicarbonate, and hypoxanthine have been added. Bovine albumin and serum-derived, lipids-cholesterol-rich mixture are then used in place of serum.
The American journal of tropical medicine and hygiene, 1993
The environment of Plasmodium falciparum gametocytes changes when they make the transition from t... more The environment of Plasmodium falciparum gametocytes changes when they make the transition from the vertebrate to the invertebrate host. Gametocytes of this species cultivated in vitro were used to evaluate the effect of serum, pH, pCO2 tension, bicarbonate ion, and temperature on gamete formation. Temperature was the only factor responsible for keeping P. falciparum gametocytes in the inactivated state. Mature gametocytes held at temperatures above 30 degrees C remained quiescent in 10% serum, even at low ambient pCO2 tension, alkaline pH, and in the presence of 25 mM bicarbonate ion. When the temperature of the medium was allowed to drop below 30 degrees C, gametocytes emerged from the red blood cells and microgametocytes consistently exflagellated at pH 7.4, even in the absence of bicarbonate ion. With regard to bicarbonate ion, exflagellation in P. falciparum is similar to P. berghei and different from P. gallinaceum gametocytes, which have an obligate requirement for bicarbonat...
The American journal of tropical medicine and hygiene, 1994
Relationships between Plasmodium falciparum incidence and entomologic inoculation rates (EIRs) we... more Relationships between Plasmodium falciparum incidence and entomologic inoculation rates (EIRs) were determined for a 21-month period in Saradidi, western Kenya, in preparation for malaria vaccine field trials. Children, ranging in age from six months to six years and treated to clear malaria parasites, were monitored daily for up to 12 weeks to detect new malaria infections. Overall, new P. falciparum infections were detected in 77% of 809 children. The percentage of children that developed infections per two-week period averaged 34.7%, ranging from 7.3% to 90.9%. Transmission by vector populations was detected in 86.4% (38 of 44) of the two-week periods, with daily EIRs averaging 0.75 infective bites per person. Periods of intense transmission during April to August, and from November to January, coincided with seasonal rains. Relationships between daily malaria attack rates and EIRs indicated that an average of only 7.5% (1 in 13) of the sporozoite inoculations produced new infect...
A breeding colony utilizing a harem mating system was established to study the feasibility of bre... more A breeding colony utilizing a harem mating system was established to study the feasibility of breeding cynomoglus monkeys, Macaca fascicularis, in Malaysia. Two groups consisting of 10 females and one male each were evaluated over a 3 period. Forty births were recorded; one was stillborn, 11 died while nursing, and 28 were weaned. The average time to wean offspring was 230 days with an average weight at weaning of 0.858 kg. The average time for conception to take place after weaning was 50 days. Of the 20 breeder females, six produced three offspring each, nine produced two offspring each, four produced one offspring each and one remained barren throughout the project. Three different weaning systems were evaluated. The best method was caging the mother-infant pair within or adjacent to the breeding room followed by a two-part cage system which allowed the infant to continue nursing and also obtain solid food inaccessible to the mother.
Journal of the American Association for Laboratory Animal Science, 2019
Many variables can influence animal behavior and physiology, potentially affecting scientific stu... more Many variables can influence animal behavior and physiology, potentially affecting scientific study outcomes. Laboratory and husbandry procedures—including handling, cage cleaning, injections, blood collection, and animal identification—may produce a multitude of effects. Previous studies have examined the effects of such procedures by making behavioral and physiologic measurements at specific time points; this approach can be disruptive and limits the frequency or duration of observations. Because these procedures can have both acute and long-term effects, the behavior and physiology of animals should be monitored continuously. We performed a retrospective data analysis on the effects of 2 routine procedures, animal identification and cage changing, on motion and breathing rates of mice continuously monitored in the home cage. Animal identification, specifically tail tattooing and ear tagging, as well as cage changing, produced distinct and reproducible postprocedural changes in sp...
Journal of the American Mosquito Control Association, 1990
The potential for Anopheles egg survival in dry soil from larval development sites was investigat... more The potential for Anopheles egg survival in dry soil from larval development sites was investigated in western Kenya. A total of 230 dry soil samples collected in 1987, 1988 and 1989 yielded 126 first-instar Anopheles gambiae s.l. larvae from 2 to 5 days after flooding with water. These larvae were from dried animal hoofprints along streams (57.9%), from dried edges of permanent and temporary pools (41.3%) and from dried stream beds (0.8%). Larval density was 1.2 larvae/kg of soil from positive microhabitats in 1987 and 2.4 larvae/kg in 1988. Thirteen larvae from the 1989 soil samples, reared to adults, were identified by DNA probes as Anopheles gambiae sensu strictu (n = 6) and Anopheles arabiensis (n = 7). Experimentally, eggs from field-collected females remained viable up to 12 days for An. gambiae s.l. and 10 days for An. funestus. In western Kenya, egg viability in dry soil may represent a significant, short-term survival mechanism for 2 species of the An. gambiae complex.
Journal of the American Mosquito Control Association
At 2 sites in western Kenya targeted for future malaria vaccine trials, adult culicine mosquitoes... more At 2 sites in western Kenya targeted for future malaria vaccine trials, adult culicine mosquitoes were sampled over one year by 5 collection techniques to assess human exposure to potential vectors of pathogens other than malaria. Collections included 20,910 females representing 19 species in Kisian and 4,312 females of 11 species in Saradidi. Common species in Kisian included Culex quinquefasciatus (71.4%), Mansonia uniformis (15.8%), Ma. africana (6.2%), Aedes mcintoshi (2.0%), Coquillettidia fuscopennata (1.9%) and Ae. ochraceus (1.8%). Common species in Saradidi included Cx. quinquefasciatus (92.7%), Cx. nebulosus (4.5%) and Ma. uniformis (1.0%). Human-bait collections identified 16 man-biting culicine species in Kisian and 9 in Saradidi. Man-biting rates at Kisian for the 5 most common species were 1.8, 14.6 and 13.5 times higher than at Saradidi for indoor, outdoor and tent collections, respectively. Exposure indoors was estimated to be 1,277 bites/man/year at Kisian and 720 a...
Journal of the American Mosquito Control Association
Floodwater Aedes breeding habitats in central Kenya were sequentially flooded to determine the nu... more Floodwater Aedes breeding habitats in central Kenya were sequentially flooded to determine the numbers of mosquito eggs hatching during each flooding. Approximately 90% of the larvae sampled during 4 floodings emerged during the initial flooding. The number of Aedes eggs hatching during the second flooding was lowest of all 4 floodings, and no significant differences in the amount of egg hatching during floodings 3 and 4 were seen. Unhatched Aedes eggs were present in soil samples collected after the final flooding. The possible implications of these findings with regard to Rift Valley fever virus control are discussed.
In rodent malaria model systems, protective immunity induced by immunization with irradiated spor... more In rodent malaria model systems, protective immunity induced by immunization with irradiated sporozoites is eliminated by in vivo depletion of CD8+ T cells, and adoptive transfer of CTL clones against the circumsporozoite protein protects against malaria. We recently demonstrated that volunteers immunized with irradiated Plasmodium falciparum sporozoites produce CTL against peptide 368-390 of the P. falciparum circumsporozoite protein. To determine whether natural exposure to malaria induced similar CTL, we studied 11 adult, male, life-long residents of a highly malarious area of Kenya, who were selected because their lymphocytes had been shown to proliferate after stimulation with peptides 361-380, 371-390, or 368-390 and because nine had been resistant to malaria in previous studies. In four of the 11 individuals there was peptide-specific, genetically restricted, CTL activity. In all four individuals, this activity was unaffected by depletion of CD4+ T cells. In three volunteers ...
Journal of the American Mosquito Control Association, 1990
Effectiveness of sustained-release Altosid pellets (4% AI methoprene) against floodwater mosquito... more Effectiveness of sustained-release Altosid pellets (4% AI methoprene) against floodwater mosquitoes in dambos treated at 5, 3, and 1 wk before and 1 day after flooding was determined. Only 2% of Aedes pupae (primarily Aedes mcintoshi) survived to adults in an area treated 5 wk preflood, and no adult mosquitoes emerged from an area treated 1 day after flooding. In contrast, 12 and 16% of Aedes pupae successfully survived to the adult stage in areas pretreated 3 and 1 wk, respectively, preflood. The effectiveness of the Altosid declined against Culex spp. (primarily Cx. antennatus) collected from dambos 15-31 days after flooding. The potential for using preflood treatment with methoprene to control Aedes vectors of Rift Valley fever virus in endemic areas is discussed.
The American journal of tropical medicine and hygiene, 1999
A two-year study was conducted of phlebotomine sand fly fauna in a defined focus of Leishmania tr... more A two-year study was conducted of phlebotomine sand fly fauna in a defined focus of Leishmania tropica. A total of 17,947 sand flies representing 10 species were collected from the location. Phlebotomus guggisbergi, a vector of L. tropica in Kenya, was the most prevalent species through the entire period, representing about 80% of the total catch. There was marked seasonal fluctuation in the populations of the three most common species, with highest population levels reached in December and lowest levels reached in July and August. Leishmania-like infections were encountered in 489 P. guggisbergi. No flagellate infections were observed in any other species of sand fly. Although infected P. guggisbergi were collected during each month of the year, the percent parous infected flies was highest (27.5%) during the November through January time period. These data show that the greatest risk of transmission to humans at this focus occurs during December, when the vector is prevalent and i...
The American journal of tropical medicine and hygiene, 1993
In the early 1930s, investigators of visceral leishmaniasis stated that Leishman-Donovan bodies a... more In the early 1930s, investigators of visceral leishmaniasis stated that Leishman-Donovan bodies are found in body fluids of kala-azar patients, for example, in urine, feces, semen, and nasal and pharyngeal secretions. Based on this finding, we investigated the diagnostic potential of nasal secretions, tonsillopharyngeal mucosal swabs, and urine centrifugates inoculated into Schneider's Drosophila Medium (containing antibiotics and antifungal agents) as well as with Giemsa-stained smears. Consequently, 64 randomly selected patients with visceral leishmaniasis from Kenya (59 who were splenic culture or Giemsa stain positive and five who were culture negative but Giemsa stain positive) were tested by three noninvasive methods. These tests were all performed before the patients were treated with Pentostam. Cultures of nasal and tonsillopharyngeal swabs and urine centrifugates produced 28 positive samples representing 24 patients (37.5%). Moreover, a set of 25 Giemsa-stained slide sm...
Journal of the American Mosquito Control Association, 1993
The effect of controlled burning on the survival of Aedes mosquito eggs was evaluated in 2 distin... more The effect of controlled burning on the survival of Aedes mosquito eggs was evaluated in 2 distinct dambo habitats. In a dambo dominated by grasses, egg survival was 3.3% after burning compared with 43.8% in a similar dambo that was not burned. In a dambo dominated by sedges, egg survival was 0.7% after burning compared with 28.5% in a similar dambo that was not burned. Mortality of mosquito eggs appeared to be caused by high temperatures associated with the fire and not elapsed time since egg survival did not decrease with time after burning. The potential for burning to control the mosquito vectors of Rift Valley fever virus is discussed.
The American journal of tropical medicine and hygiene, 1993
The elimination of serum from Plasmodium falciparum culture media could decrease costs, enhance p... more The elimination of serum from Plasmodium falciparum culture media could decrease costs, enhance procurement, and improve the feasibility of large-scale production of parasite material. We provide a semi-defined, serum-free formulation, of commercially available constituents that supports P. falciparum parasite growth at rates comparable with those obtained with serum-supplemented media. The medium is composed of RPMI 1640 to which HEPES, extra glucose, bicarbonate, and hypoxanthine have been added. Bovine albumin and serum-derived, lipids-cholesterol-rich mixture are then used in place of serum.
The American journal of tropical medicine and hygiene, 1993
The environment of Plasmodium falciparum gametocytes changes when they make the transition from t... more The environment of Plasmodium falciparum gametocytes changes when they make the transition from the vertebrate to the invertebrate host. Gametocytes of this species cultivated in vitro were used to evaluate the effect of serum, pH, pCO2 tension, bicarbonate ion, and temperature on gamete formation. Temperature was the only factor responsible for keeping P. falciparum gametocytes in the inactivated state. Mature gametocytes held at temperatures above 30 degrees C remained quiescent in 10% serum, even at low ambient pCO2 tension, alkaline pH, and in the presence of 25 mM bicarbonate ion. When the temperature of the medium was allowed to drop below 30 degrees C, gametocytes emerged from the red blood cells and microgametocytes consistently exflagellated at pH 7.4, even in the absence of bicarbonate ion. With regard to bicarbonate ion, exflagellation in P. falciparum is similar to P. berghei and different from P. gallinaceum gametocytes, which have an obligate requirement for bicarbonat...
The American journal of tropical medicine and hygiene, 1994
Relationships between Plasmodium falciparum incidence and entomologic inoculation rates (EIRs) we... more Relationships between Plasmodium falciparum incidence and entomologic inoculation rates (EIRs) were determined for a 21-month period in Saradidi, western Kenya, in preparation for malaria vaccine field trials. Children, ranging in age from six months to six years and treated to clear malaria parasites, were monitored daily for up to 12 weeks to detect new malaria infections. Overall, new P. falciparum infections were detected in 77% of 809 children. The percentage of children that developed infections per two-week period averaged 34.7%, ranging from 7.3% to 90.9%. Transmission by vector populations was detected in 86.4% (38 of 44) of the two-week periods, with daily EIRs averaging 0.75 infective bites per person. Periods of intense transmission during April to August, and from November to January, coincided with seasonal rains. Relationships between daily malaria attack rates and EIRs indicated that an average of only 7.5% (1 in 13) of the sporozoite inoculations produced new infect...
A breeding colony utilizing a harem mating system was established to study the feasibility of bre... more A breeding colony utilizing a harem mating system was established to study the feasibility of breeding cynomoglus monkeys, Macaca fascicularis, in Malaysia. Two groups consisting of 10 females and one male each were evaluated over a 3 period. Forty births were recorded; one was stillborn, 11 died while nursing, and 28 were weaned. The average time to wean offspring was 230 days with an average weight at weaning of 0.858 kg. The average time for conception to take place after weaning was 50 days. Of the 20 breeder females, six produced three offspring each, nine produced two offspring each, four produced one offspring each and one remained barren throughout the project. Three different weaning systems were evaluated. The best method was caging the mother-infant pair within or adjacent to the breeding room followed by a two-part cage system which allowed the infant to continue nursing and also obtain solid food inaccessible to the mother.
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Papers by Clifford Roberts