Dirofilaria immitis is a mosquito-borne nematode-causing canine heartworm disease, with adult worms localized in the pulmonary arteries and right heart. In rare cases, ectopic migration might occur, and adults and blood circulating microfilariae can be found in unusual organs or fluids (e.g., eyes, abdominal cavity, bone marrow, and urine). A 17-year-old mixed-breed female dog was presented in a private veterinary clinic in Italy for hematuria and dysuria. Physical examination showed cardiac mitral murmur with marked respiratory distress and cyanotic mucous membranes after handling. Abdominal ultrasounds revealed a non-specific chronic cystopathy, while the echocardiography showed enlargement of the right heart associated with tricuspid insufficiency and mitral regurgitation, with the presence of an adult filariae in the right ventricular chamber. Circulating microfilariae were observed in the blood smear and molecularly identified as D. immitis. Unusual microfilaruria was detected in the urine sediment. Data presented raise awareness about the occurrence of microfilariae in unusual locations, such as the bladder, suggesting the need of a thorough clinical and laboratory assessment where D. immitis is endemic.

The aim of this study was to evaluate the efficacy of a topical combination of moxidectin 3.5%, imidacloprid 10% and praziquantel 10% for the prevention of Dirofilaria immitis (Leidy, 1856) infection in dogs. For this purpose, a randomized and controlled clinical trial was conducted between August 2021 and October 2022, in the municipality of Goiana, state of Pernambuco, north-eastern Brazil, where heartworm is highly prevalent. Of the 213 dogs initially sampled (baseline), 68 (31.9%) were positive for adult antigens (SNAP 4Dx Plus, Idexx) and/or microfilariae (modified Knott\'s test). On day 0, 140 negative dogs were randomly included in the treatment and control groups, 70 animals each. During the study, 60 dogs (34 treated and 26 untreated) were removed for different reasons. At the end of the study (day 360 ± 2), 36 treated and 44 untreated were sampled and included in the efficacy calculation. The efficacy against the development of adults and microfilariae was 84.7%, with only one treated dog being positive for adult antigens but negative for microfilariae. On the other hand, eight untreated dogs were positive for adult antigens and/or microfilariae, resulting in a significant difference in the number of positives between groups (Chi-square test = 4.706, df = 1, P = 0.0301). Remarkably, the efficacy against the appearance of D. immitis microfilariae was 100% (i.e., all treated dogs negative) and three untreated dogs were positive for microfilariae. The topical combination of moxidectin 3.5%, imidacloprid 10% and praziquantel 10% significantly reduced the risk of D. immitis infection in treated dogs as compared with untreated dogs, in a highly endemic area in north-eastern Brazil.

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OBJECTIVE: To make a survey on the possible imported cases with microfilaremia from a recently identified outbreak focus in Fuchuan County of Guangxi Region.
METHODS: Moving people as temporary laborers from Guangxi and periphery residents were screened by thick blood smears for microfilariae and ELISA for specific IgG4 in Sept 2007.
RESULTS: 989 persons in cities/districts of Nansha, Panyu, Shantou and Zhongshan were investigated. Among 150 persons from Changtang administrative village of Guangxi, 47 were from two outbreak focuses, Ganshang and Yinshan natural villages in Changtang. Three cases with microfilaremia were found, with a microfilaraemia density of 24, 20 and 2 per 120 microl blood, respectively. The 3 cases were all from the 2 natural villages, with a microfilaraemia positive rate of 6.4% (3/47). Meanwhile, anti-filaria IgG4 was detected for other 1 501 persons, including those from the outbreak focuses, from surr-founding areas and from non-endemic area as control, fifteen cases were found with IgG4 positive. Of the 15 positive cases, 12 were from the 2 outbreak natural villages, with a positive rate of 25.5%, higher than those of others (chi2=295.83, P < 0.01). The cases with IgG4 positive but microfilaremia negative were reexamined by ICT kit and all showed negative.
CONCLUSIONS: It is suggested that no further transmission occurs although microfilaremia cases have been imported from the outbreak focus of Guangxi.

OBJECTIVE: To describe the discovery of a residual foci of bancroftian filariasis in Fuchuan County where the disease was announced to have been eliminated, and reveal its epidemiologic feature.
METHODS: The investigation was carried out from August 2007 to March 2008 among residents in Changtang village where the first case of filariasis was found and the neighboring villages. They were screened with two thick blood smears. Immunochromatographic technology (ICT) was conducted for those going out but returned and those in surrounding areas. Vector mosquitoes were collected and dissected to find filaria larvae. Historical documents were reviewed and relevant people were interviewed.
RESULTS: In Changtang administrative village, 1052 residents were screened and 19 cases with microfilaremia were found in 2 natural villages, with a Mf-positive rate of 1.8% (5.1% in Gangshang and 1.4% in Yinshan respectively). No Mf-positive case was found in 4119 residents screened in other 3 villages. The average microfilaria density in the 19 cases was 17.37/60 +/- 1 blood. All the 19 cases belonged to 12 families, and 13 cases were relatives to each other, which showed a feature of spatial clustering and family clustering. More patients were identified in the age groups of 20-29 and 50-59, and 57.9% of them were older than 50 years. No larvae were found in 54 Culex pipiens fatigans dissected.
CONCLUSIONS: The Changtang village is identified as a residual focus of bancroftian filariasis with a low, limited endemicity. More cases have been among the elderly with a low average microfilaremia.

OBJECTIVE: To investigate the density fluctuation of microfilariae, persistence of microfilaremia and possible new infection due to residual microfilaremia in areas with filariasis transmission interrupted.
METHODS: The observation site was made in a village of Jishou City, Hunan Province. Inhabitants were regularly examined by thick blood smear and the density fluctuation of residual microfilaremia in known and newly-found cases were followed up. With a consent from the cases with residual microfilaremia, no treatment was given until they naturally turned negative. Antifilarial antibody level was detected by IFAT and a test kit for filariasis-special IgG4. Culex quinquefociatus was dissected to determine the natural infection rate and density of III stage filarial larvae in transmission season. The identified cases were followed-up by interviews and physical examinations to see if clinical manifestations appeared.
RESULTS: Blood examination was carried out for all inhabitants for 10 times, 4 cases with microfilaremia, including 3 cases found at the beginning of the project and one newly infected case, were discovered after the interruption of filariasis transmission in the 19-year period. Among the 4 cases followed up, one case naturally turned negative within 7 years, one case became negative in the 9th year but returned positive in the 12th year, and then naturally turned negative in the 13th year. The 3rd case turned negative in the 14th year and was again positive in the 19th and the 20th years, and became negative through diethylcarbamazine (DEC) treatment in the 21st year. The new case was found to have microfilaremia in the 16th year and kept positive for 5 years until DEC treatment. Serological tests (IFAT and special IgG4) revealed no new positive cases. The natural infection rate and larvae density in Culex quinquefasciatus decreased annually. Conclusion The persistence period of residual microfilaremia in individual cases might last for more than 20 years after filariasis transmission has been interrupted.

Zoucheng was a high endemic area of bancroftian filariasis with Culex pipiens pallens as the principal transmitting vector. Transmission of the disease was interrupted in 1981. Epidemiological surveillance has been then carried out. After 1989, parasitological and immunological examinations were conducted for those cases previously with and without microfilaremia, entomological surveillance was also carried out. Results showed that the antibody level in inhabitants has been at normal level, and no infection has been found in mosquitoes.

OBJECTIVE: To investigate a new way to detect filarial larvae in mosquitoes and apply it to the surveillance of filariasis.
METHODS: An oligonucleotide probe that was species-specific to W. malayi was synthesized and marked with 32P using molecular biological technique. Then the probe was tested with dot hybridization in detection of W. malayi filarial larvae from mosquitoes.
RESULTS: The minimal detectable limit was found to be 2 ng DNA of filarial larvae or microfilaria (Mf.), with no cross reaction with other animal filariae. A single larva can be detected when infected mosquitoes were tested one by one. One infected mosquito can be detected from a group of 20 mosquitoes tested together.
CONCLUSIONS: Our probe is sensitive and specific. It is practical to apply our probe to mosquito surveillance in Brug\'s filariasis endemic areas.

OBJECTIVE: To elucidate the transmission dynamic and epidemic trend of bancroftian filariasis occurred under the condition with no control measure taken 5 years after elimination of filariasis.
METHODS: A 10-year longitudinal observation (from 1984 to 1994) was made in Huayuan Village in Shengli Township of Tancheng County, which used to be a high bancroftian filariasis-endemic area in southern part of Shandong Province.
RESULTS: The microfilarial rate decreased from 0.56% before the study to 0.12% after the study and 8 out of the 9 previous microfilaria-positive cases became negative gradually. During the study period, 6 new microfilaremia cases were detected, 5 of which became negative naturally within 3 to 4 years. Eighty-eight point eight nine per cent of the detected patients with microfilaremia converted into IgG4-negative after 10 years. The natural infective rate of vectors decreased year by year and became zero by the tenth year of the study, the annual transmission potency decreased also from 3.47 to zero by the tenth year.
CONCLUSIONS: It showed that under the local natural environment the biting rate representing the vector density which was obtained by capture method was from 24.1 to 52.5 person/night among the residents who did not use mosquito nets, and 13.5 to 21 person/night among the residents who used mosquito nets. The microfilarial rate of 0.56% in population with the average microfilarial density of 6.6 to 20.7 capita/60 microliters ear blood of residual microfilaria-positive patients might be considered as the terminal threshold of transmission.

OBJECTIVE: To study the regular pattern of growth and declination or the transmission potential of filariasis after the disease was basically (the microfilarial rate was lower than 1%) in Henan Province in 1987.
METHODS: According to the distribution of filaria species and original microfilarial rate, in 7 surveillance sites in 7 counties (cities) the etiology and mosquito vector surveys were carried out continuously during 1988-1995 and no control measurement for pathogen was taken.
RESULTS: Ten residual microfilaremias became negative gradually in the first 6 years and no new microfilaremias occurred during 1988-1995. During 1993 to 1995, the microfilaremias rate of population in the sites was 0. The natural infection rates of filarial larvae in vector mosquito were 0.1%-0. During the 8 years, 15 vector mosquitos were positive with a total of 18 filarial larvae which were all of first or second-stage larvae. The C. pipiens pallens was the main vector, the second was A. sinensis, with a small number of C. fatigans and A. anthropophagus. The man-biting rates of mosquitoes for outdoor sleepers fluctuated greatly, the highest one was 360.6 mosquitoes/person per night and the lowest, 7.2. The man-biting rates of mosquitoes for sleepers inside mosquito-net was about 1 mosquito/person per night. The proportion of multiparous mosquitoes also fluctuated more greatly, the highest one was 88.1% and the lowest 27. 2% According to the data described above, the man-biting rate of vector mosquito which contained filarial L3 was 0.
CONCLUSIONS: The results suggested that after the microfilarial rate was lower than 1%, the residual microfilaremias became negative gradually in 3-6 years, and the transmission of the disease was blocked. Therefore, in the areas where filariasis was basically controlled, elimination of the disease was attainable within sight.